Vehicle equipment control with semiconductor light sensors

ABSTRACT

Equipment on automotive vehicle ( 20 ) is controlled by a system at least one semiconductor light sensor ( 170, 170 ′) having variable sensitivity to light. Each light sensor generates a light signal ( 164 ) indicative of the intensity of light incident on the light sensor. Control logic ( 66 ) varies the sensitivity of the light sensor and generates equipment control signals ( 166 ) based on received light signals. Sensitivity of light sensors ( 170, 170 ′) may be varied by changing the integration time ( 228 ) for producing charge from light ( 176 ) incident on light transducers ( 178 ), by selecting between light transducers ( 178, 490, 500, 504 ) of different sensitivity within the light sensor ( 170 ), by using a light transducer ( 530 ) with a sensitivity that is a function of the amount of incident light ( 176 ), and the like. Controlled equipment includes devices such as automatically dimming rearview mirrors ( 24,26 ), headlamps ( 44 ), and moisture removal means ( 38, 40, 42 ).

REFERENCE TO RELATED APPLICATIONS

This is a Continuation-in-Part of co-pending U.S. patent applicationSer. No. 09/307,941, entitled AUTOMATIC DIMMING MIRROR USINGSEMICONDUCTOR LIGHT SENSOR WITH INTEGRAL CHARGE COLLECTION, May 7, 1999,which is a Continuation-in-Part of U.S. patent application Ser. No.09/236,969, entitled AUTOMATIC DIMMING MIRROR USING SEMICONDUCTOR LIGHTSENSOR WITH INTEGRAL CHARGE COLLECTION, filed Jan. 25, 1999, thedisclosures of which are incorporated herein by reference thereto. Thisapplication is also a Continuation-in-Part of co-pending U.S. patentapplication Ser. No. 09/307,191, entitled PHOTODIODE LIGHT SENSOR, filedMay 7, 1999, and a Continuation-in-Part of co-pending U.S. patentapplication Ser. No. 09/290,966, entitled MOISTURE DETECTING SYSTEMUSING SEMICONDUCTOR LIGHT SENSOR WITH INTEGRAL CHARGE COLLECTOR, filedApr. 13, 1999, both of which are a Continuation-in-Part of U.S. patentapplication Ser. No. 09/237,107, entitled PHOTODIODE LIGHT SENSOR, filedJan. 25, 1999, the disclosures of all of which are incorporated hereinby reference thereto.

TECHNICAL FIELD

The present invention relates to automatically controlled automotivevehicle equipment of the type using light sensors to monitor lightlevels.

BACKGROUND ART

The continuing reduction in the size and cost of electronic circuits, inparticular microprocessors, makes possible the inclusion of anincreasing amount of intelligence for the automatic control ofautomotive vehicle equipment. Examples include: rearview mirrors thatadjust their reflectivity in response to the levels of ambient light andglare from other vehicles; moisture on windows sensed and removed byautomatic wipers, defrosters, defoggers, and the like; windows thatautomatically close when rain is detected; headlamps switched inresponse to ambient light levels; heating and cooling of the vehiclepassenger compartment automatically adjusted in anticipation of changesin external conditions.

Systems that automatically control automotive equipment canadvantageously employ one or more sensors for measuring light levels.Automatically dimmable rearview mirrors, and in particularelectrochromic mirrors, using light sensors, are described in U.S. Pat.No. 4,902,108 to Byker; U.S. Pat. No. 5,724,187 to Varaprasad et al.;and U.S. Pat. No. 5,928,572 to Tonar et al.; as well as U.S. patentapplication Ser. No. 08/832,596 to Baumann et al., filed Apr. 2, 1997,entitled “An Improved Electrochromic Medium Capable of Producing APre-Selected Color.” In the case of mirrors having automaticreflectivity control, such as electrochromic mirrors, it is advantageousto use sensors to detect both forward and rear light levels. Among thedual sensor designs proposed include those described in U.S. Pat. No.3,601,614 to Platzer; U.S. Pat. No. 3,746,430 to Brean et al.; U.S. Pat.No. 4,580,875 to Bechtel et al.; U.S. Pat. No. 4,793,690 to Gahan etal.; U.S. Pat. No. 4,886,960 to Molyneux et al.; U.S. Pat. No. 4,917,477to Bechtel et al.; U.S. Pat. No. 5,204,778 to Bechtel; U.S. Pat. No.5,451,822 to Bechtel et al.; and U.S. Pat. No. 5,715,093 to Schierbeeket al. A vision system is disclosed in U.S. patent application Ser. No.09/001,855, entitled VEHICLE VISION SYSTEM, filed by Jon H. Bechtel etal. on Dec. 31, 1997, the disclosure of which is incorporated herein byreference thereto.

Various moisture detectors are also known that employ a light sensor.Examples of such detectors include those described in U.S. Pat. No.5,821,863 to Schröder et al.; U.S. Pat. No. 5,796,106 to Noack; U.S.Pat. No. 5,661,303 to Teder; U.S. Pat. No. 5,386,111 to Zimmerman; U.S.Pat. No. 4,973,844 to O'Farrell et al.; U.S. Pat. No. 4,960,996 toHochstein; U.S. Pat. No. 4,930,742 to Schofield et al.; U.S. Pat. No.4,871,917 to O'Farrell et al.; U.S. Pat. No. 4,867,561 to Fujii et al.;U.S. Pat. No. 4,798,956 to Hochstein; U.S. Pat. No. 4,652,745 toZanardelli; and U.S. Pat. No. RE. 35,762 to Zimmerman. A moisturedetection system is disclosed in U.S. Pat. No. 5,923,027, entitledMOISTURE SENSOR AND WINDSHIELD FOG DETECTOR USING AN IMAGE SENSOR,issued on Jul. 13, 1999, to Joseph S. Stam et al., the disclosure ofwhich is incorporated herein by reference thereto.

A variety of systems for controlling headlamps using a light sensor arealso known, including those described in U.S. Pat. No. 4,891,559 toMatsumoto et al.; U.S. Pat. No. 5,036,437 to Macks; U.S. Pat. No.5,235,178 to Hegyi; U.S. Pat. No. 5,537,003 to Bechtel et al.; U.S. Pat.No. 5,416,318 to Hegyi; U.S. Pat. No. 5,426,294 to Kobayashi et al.;U.S. Pat. No. 5,666,028 to Bechtel et al., and U.S. Pat. No. 5,942,853to Piscart. Such systems employ a light sensor to detect conditionsunder which the headlamp light intensity is altered. Other systems aredisclosed in U.S. Pat. No. 5,837,994, entitled CONTROL SYSTEM TOAUTOMATICALLY DIM VEHICLE HEAD LAMPS, issued Nov. 17, 1998, to JosephScott Stam et al., U.S. Pat. No. 5,990,469, entitled CONTROL CIRCUIT FORIMAGE ARRAY SENSORS, issued to Jon H. Bechtel et al. on Nov. 23, 1999,and U.S. Pat. No. 5,998,929, entitled CONTROL SYSTEM FOR AUTOMOTIVEVEHICLE HEADLAMPS AND OTHER VEHICLE EQUIPMENT, issued on Dec. 7, 1999,to Jon H. Bechtel et al, the disclosures of which are incorporatedherein by reference thereto.

Such automatically controlled equipment may employ one or more cadmiumsulfide (CdS) cell as a light sensor. CdS cells are photosensitiveresistors exhibiting increasing conductance with increasing lightlevels. CdS cells offer some advantages, such as being relatively low incost, demonstrating good sensitivity to low light levels, and providinga spectral response somewhat similar to that of the human eye. However,equipment employing such cells can not fully realize these advantagesdue to other characteristics of CdS cells, such as: a high degree ofvariance between cells, slow response at low light levels, poorenvironmental stability, limited dynamic range, and difficulty beingassembled in automated electronic manufacturing processes and equipment.Rearview mirrors employing CdS cells for sensing ambient light and glaremay incorporate the CdS cell into a full or partial bridge to increasethe dynamic range of the cell. However, the bridge output will onlyrepresent a fixed relationship between an ambient light level and aglare level, which fixed relationship is often not appropriatethroughout the range of ambient light levels monitored.

Vehicle equipment, such as automatic dimming mirrors, have also used oneor more discrete photodiodes configured as a light-dependent currentsource. Relative to equipment using CdS cells, equipment usingphotodiodes will experience less operational variance due to the lightsensor part performance, will demonstrate better environmentalstability, and will be more easily adapted to automated manufacturing.However, photodiodes themselves are relatively expensive and producevery low currents at low light levels. These low currents require theinclusion of special amplification techniques to achieve a useful signalfor the electronic components, increasing the cost and complexity of theequipment.

Another approach to providing equipment responsive to ambient light isdescribed in U.S. Pat. No. 5,760,962 issued to Schofield et al. whereinan automatically dimmable mirror is disclosed that incorporates a largeimaging array to gather light from behind and beside the vehicle. Eachlight transducer, or pixel, within the array views a separate areawithin the target spatial distribution of the light sensor. Theequipment measures ambient light by examining pixels generally directedsideways. The cost of the imaging array, the required lens, and thecomplicated signal processing logic make equipment using the imagingarray prohibitively expensive for many automotive applications. Anadditional problem is that light collected from a side view lessaccurately represents the ambient light experienced by the vehicleoperator than does light from a forward view.

One difficulty with providing equipment employing light sensors is theoccurrence of operating anomalies when the equipment is subject to hightemperatures. Some equipment employs light sensors that are extremelynon-linear at high temperatures. Other equipment may suffer a permanentchange in operating characteristics after being exposed to hightemperatures. Such a permanent change can occur in equipment using a CdScell exposed to prolonged sun on a hot day, such as prolonged exposureto temperatures in excess of 87 C. Sensors may even provide completelyfalse readings, such as by identifying a bright light condition in lowlight conditions, due to excessive thermal noise. Traditionally, theonly way to deal with this problem has been to incorporate a temperaturesensor and additional electronics into the vehicle equipment tocompensate for sensor performance changes resulting from temperaturevariations. Such electronics add cost and complexity to the equipment.

It can thus be seen that a difficulty with implementing automaticallycontrolled equipment is accommodating the light sensor. Inclusion oflight sensors typically introduces complex and costly manufacturingprocesses. However, the equipment needs to be inexpensive to fall withinthe range deemed acceptable by an automobile purchaser. Additionally,manufacturers of vehicles incorporating such equipment must eitheraccept inconsistent operating performance or use complex and costlycircuitry and processes to accommodate these variations. Such additionalprovisions may be required to enable the equipment to operate withsufficiently consistent sensitivity across a wide dynamic range as isrequired for operation in the ranges of temperature, humidity, shock,and vibration experienced within a vehicle.

What is needed is more cost-effective equipment using light sensorsoperable over a wide range of light conditions and temperatures.

SUMMARY

Automotive vehicle equipment is controlled by a system including atleast one semiconductor light sensor having variable sensitivity tolight. A light sensor generates a light signal indicative of theintensity of light incident on the light sensor. Control logic variesthe sensitivity of light sensors and generates equipment control signalsbased on received light signals. Sensitivity of light sensors may bevaried by changing the integration time of charge produced by lightincident on light transducers, by selecting between light transducers ofdifferent sensitivity within the light sensor, by using a lighttransducer with a sensitivity that is a function of the amount ofincident light, and the like.

In one embodiment, the system for automatically controlling vehicleequipment includes at least one semiconductor light sensor outputting adiscrete light signal based on light incident over a variableintegration period. Control logic generates at least one equipmentcontrol signal based on the discrete light signal.

In another embodiment, the vehicle equipment includes a rearview mirrorhaving a dimming element with a variably reflective surface, the degreeof reflectivity based on the equipment control signal. The light sensorsinclude at least one of an ambient light sensor positioned to receivelight generally in front of the vehicle and a glare sensor positioned toview a scene generally behind a vehicle operator.

In still another embodiment, the vehicle equipment includes at least oneheadlamp. The light sensors include at least one ambient light sensorpositioned to receive light generally in front of and above the vehicle.The light sensors may be a first ambient light sensor admitting light ina first band of frequencies and a second ambient light sensor admittinglight in a second band of frequencies different than the first band offrequencies. The control logic can determine a first filtered ambientlight level from the light signal output from the first ambient lightsensor and a second filtered ambient light level from the light signaloutput from the second ambient light sensor. A threshold based on thefirst filtered ambient light level and the second filtered ambient lightlevel is found. A headlamp control signal based on the threshold and atleast one of the first filtered ambient light levels and the secondambient light level is generated.

In yet another embodiment, the control of vehicle equipment is based ondetecting the presence of moisture on a window. The system includes anemitter for emitting light at the window. At least one light sensor ispositioned to receive light from the emitter reflected from the window.The control logic receives a first light signal from the light sensorwith the emitter turned off. The emitter is turned on and a second lightsignal is received from the light sensor. The presence of moisture isdetermined based on the first light signal and the second light signal.

A method for automatically controlling equipment in an automotivevehicle is also disclosed. Sensitivity is determined for at least onesemiconductor light sensor. Charge incident on the light sensor isintegrated to achieve the determined sensitivity. A discrete lightsignal is generated based on the light incident on the light sensor overthe integration period. The discrete light signal can be analog ordigital. In one embodiment, the discrete signal has a digital level witha variable, analog length. At least one vehicle equipment control signalis then generated based on the discrete light signal.

These and other objects, features, and advantages will be apparent fromreading the following detailed description taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a top plan view of an automotive vehicle that may incorporateautomatically controlled equipment;

FIG. 2 is a top, rear perspective view of a rearview mirror including aforward ambient hight sensor and a skyward ambient light sensor;

FIG. 3 is a top, rear perspective view of a rearview mirror circuitboard for the rearview mi according to FIG. 2;

FIG. 4 is a block diagram illustrating a generalized automatic vehicleequipment control system;

FIG. 5 is schematic diagram of circuitry permitting control logic and alight sensor to be interconnected by a single line carrying bothsensitivity control and sensor output;

FIG. 6 is a timing diagram illustrating operation of the circuitry ofFIG. 5;

FIG. 7 is a timing diagram illustrating integration duration control andsensor output for a light sensor;

FIG. 8 is a schematic diagram illustrating operation of a light sensorhaving a pulse output;

FIG. 9 is a timing diagram illustrating operation of the light sensor ofFIG. 8;

FIG. 10 is a schematic diagram illustrating operation of a light sensorwith noise compensation;

FIG. 11 is a timing diagram illustrating operation of the light sensorof FIG. 10;

FIG. 12 is a schematic diagram illustrating an implementation of thelight sensor of FIG. 14 using photodiodes as light transducers;

FIG. 12a is a circuit schematic of an alternate circuit for convertingthe LIGHT and NOISE signals of FIG. 12 to an output signal;

FIGS. 13-16 are block diagrams illustrating various embodiments forlight sensor packaging, output, and control;

FIG. 17 is a block diagram illustrating sensor logic for internallydetermining the integration period signal;

FIG. 18 is a block diagram illustrating the use of light transducershaving different effective areas to achieve differing sensitivity;

FIG. 19 is a block diagram illustrating the use of light transducershaving different apertures to achieve increased dynamic range;

FIG. 20 is a schematic diagram illustrating different transducercapacitances for different amounts of light-induced charge to achievevariable sensitivity;

FIG. 21 is a graph of the output potential as a function of accumulatedincident light for the transducer of FIG. 20;

FIG. 22 is a schematic diagram illustrating a photodiode transducerincorporating an anti-bloom gate;

FIG. 23 illustrates an enclosure for a light sensor;

FIG. 24 illustrates a light sensor field of view as a function of lighttransducer distance from the lens;

FIG. 25 is a graph illustrating light sensor optical gain as a functionof light transducer distance from the lens;

FIG. 26 is a perspective view illustrating an alternate light sensor;

FIG. 26a is a side elevation view illustrating of the sensor accordingto FIG. 26;

FIG. 27 is a graph illustrating frequency responses of the human eye;

FIG. 28 is a graph illustrating frequency response of a typical lighttransducer;

FIG. 29 is a drawing of an enclosure incorporating an infrared filter;

FIGS. 30a-30 d illustrate a side view of the light sensor die at fourstages during the direct depositing of a film on a sensor transducer;

FIG. 31 is a graph of the frequency response of a window film that maybe used to implement a light sensor filter;

FIG. 32 is a graph of the frequency response of a light sensorincorporating the window film with the frequency response shown in FIG.31.

FIG. 33 is a block diagram illustrating circuitry for an automaticallydimmed rearview mirror;

FIG. 34 is a block diagram illustrating a rearview mirror system withinterior and exterior rearview mirrors;

FIG. 35 is a schematic diagram illustrating an embodiment of controllogic for an automatically dimming interior rearview mirror;

FIG. 36 is a schematic diagram illustrating operation of electro chromicelement transmittance control;

FIG. 37 is a timing diagram illustrating electrochromic elementtransmittance control;

FIG. 38 is a graph indicating dimmer reflectance as a function of dimmercontrol signal duty cycle;

FIG. 39 is a flow diagram illustrating operation of automaticallydimming rearview mirror control logic;

FIG. 40 is a graph illustrating binary logarithmic approximationimplemented in an embodiment of control logic for an automaticallydimming rearview mirror;

FIG. 41 is a block diagram illustrating equipment for detecting thepresence of moisture on a vehicle window;

FIG. 42 is a ray diagram illustrating moisture detection on an outsidesurface causing an increase in reflected light;

FIG. 43 is a ray diagram illustrating moisture detection on an outsidesurface causing a decrease in reflected light;

FIG. 44 is a flow diagram illustrating operation of control logic forautomatically removing moisture from a vehicle window;

FIG. 45 is a block diagram illustrating circuitry for controllingheadlamps;

FIG. 46 is a graph illustrating the differences in the spectral contentof ambient light on a cloudy day and ambient light on a clear day;

FIG. 47 is a flow diagram illustrating operation of control logic forautomatically controlling vehicle headlamps;

FIG. 48 is a chart illustrating wavelength responsivity of a filter thatcan be advantageously utilized for the headlight dimmer sky sensor;

FIG. 49 is a polar iso-candela plot of the light sensor according toFIGS. 26 and 26a having a cylindrical lens; and

FIG. 50 is a rectangular iso-candela plot according to FIG. 49 viewedorthogonally to the longitudinal axis of the cylindrical lens.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to FIG. 1, an automotive vehicle 20 is shown. Vehicle 20is driven by operator 22. Operator 22 uses interior rearview mirror 24and one or more exterior rearview mirrors 26 to view rearward scenes,shown generally by 28. Most of the time, operator 22 looks forwardthrough windshield 30. The eyes of the operator 22 therefore adjust toforward ambient light 32 coming generally from the front of the vehicle.In low ambient light conditions, a relatively bright light source inrearward scene 28 may reflect from mirrors 24,26 and temporarilyvisually impair, distract, or dazzle operator 22. This relatively stronglight is known as glare 34.

To reduce the impact of glare 34 on operator 22, the reflectance ofmirrors 24,26 may be reduced. Manually adjustable interior mirrorscontain a prismatic reflective element manually switched by operator 22to change the amount of light that mirror reflects to operator 22.Automatically dimming interior and exterior mirrors 24, 26 includeelements that automatically adjust the amount of light reflected tooperator 22 responsive to the detected level of glare 34. Automaticallydimming mirrors include a light sensor for glare 34 and, typically, alight sensor for forward ambient light 32.

Another environmental condition that can have an affect on operator 22is moisture, which may condense on or impact vehicle windows, such aswindshield 30 or rear window 36. Such moisture can impair the view ofoperator 22. This moisture may take the form of rain, snow, sleet, andthe like on a window exterior surface, or may be fog, frost, ice, andthe like on a window exterior or interior surface. Vehicle 20 typicallyincludes several means for removing moisture, such as wipers 38 forwindshield 30 and, possibly, rear window 36, defoggers 40 built into thedashboard of vehicle 20, and defrosters 42 built into rear window 36, orpossibly windshield 30. Typically, this moisture removing equipment ismanually controlled. In order to automatically control such moistureremoving means, the presence of moisture on vehicle windows 30, 36 mustbe properly detected. Light sensors can be used to detect the moisture.

Other vehicle equipment requiring control are headlamps 44 thatilluminate an area in front of vehicle 20 when ambient conditions do notprovide sufficient light. Manual controls for the headlamps, parkinglights, and bright lights, are well known. Headlamps 44 may also beautomatically varied between off or daylight running light settings andnight time light beams based on the level of ambient light detected by alight sensor (not shown in FIG. 1). Since most ambient lightilluminating the forward view of operator 22 comes from above vehicle20, skyward ambient light 46 from a direction generally in front of andabove vehicle 20 may advantageously be monitored for automaticallycontrolling headlamps 44.

Other vehicle equipment may also be controlled responsive to lightsensors. Openings such as power door windows, sunroofs, moon roofs,convertible tops, and the like can be automatically closed when rain isdetected. Passenger compartment heating and cooling may be improved byanticipating changes in thermal loading, such as when the sun disappearsbehind or appears from a cloud bank, or detecting which side of thevehicle is in the sun. Parking lamps, puddle lights, courtesy lights,and other auxiliary lighting may be controlled based on ambient lightlevels, the detected presence of exterior moisture, the running state ofvehicle 20, and the like. Fog lights on the front and/or rear of thevehicle can be controlled based on the detection of fog. Whileparticular applications, such as rearview mirror dimming, moistureremoval, and headlamp control, are described in detail herein, it isunderstood that the present invention applies to a wide variety ofautomatic equipment control within automotive vehicles. Accordingly, asused herein, “vehicle equipment” refers to power windows, power doors,sunroofs, moon roofs, convertible tops, running lights, fog lights,parking lights, puddle lights, courtesy lights, and other vehiclelights, rearview mirrors, heating and cooling systems, windshieldwipers, and headlamps, and any other controlled mechanism or componentsin a vehicle.

Regardless of the vehicle equipment controlled, automotive consumerswill welcome such automated control of equipment provided the equipmentmeets certain criteria. First, the automatic equipment works in areasonable and predictable manner throughout the wide range of operatingconditions experienced by an automotive vehicle. Second, the equipmentoperates reliably throughout the life of the vehicle. Third, theequipment is reasonably priced. Forth, the automatic equipment frees thedriver to concentrate on driving.

The light sensors, and also possibly the control logic, for theautomatically controlled equipment can be advantageously implemented ininterior rearview mirror 24. The review mirror provides an excellentlocation for light sensors as it is located high in the vehiclepassenger compartment at a location with a good field of view throughthe side windows, the front windshield 30, and the rear window 36. Theinterior rearview mirror 24 includes a forward ambient light sensor 58(FIG. 2), skyward ambient light sensors 150, 150′, 158, 158′, glaresensor 62 (FIG. 3), light emitter 104, a first reflected light sensor110, and a second reflected light senor 110 a. Interior rearview mirror24 includes housing 850 into which these light sensors are assembled.Forward ambient light sensor 58 is held within housing 850 so as to viewforward ambient light 32. One or more skyward ambient light sensors 150,150′, 158, 158′ are held within housing 850 so as to view skywardambient light 46. Although four skyward ambient light sensors areillustrated, a single sky sensor 150 or two light sensors 150, 158 canbe used to monitor the forward sky ambient light 46.

Housing 850 may be formed so as to restrict light collected by skywardambient light sensors 150, 150′, 158, 158′. In particular, skywardambient light sensors 150, 150′, 158, 158′ may be recessed into housing850 to limit the amount of forward ambient light 32 received by lightsensors 150, 150′, 158, 158′. Similarly, forward ambient light sensor 58may be recessed in housing 850 to limit the amount of skyward light 46impacting this sensor. Housing 850 is attached to a mirror mountingassembly, shown generally by 852. Mounting assembly 852 includesmounting foot 854 for attaching rearview mirror 24 to windshield 30. Themounting foot may be attached to windshield 30 using a clear adhesive.Moisture sensor 120 may be incorporated into mounting foot 854. Inaddition or alternatively, one or more of forward ambient light sensor58, skyward ambient light sensor 150, and skyward ambient light sensor158 may be incorporated into mounting foot 854. By locating sensors 150,158 in mounting foot 854, sensors 150′, 158′ can be omitted.

Referring now to FIG. 3, the rearview mirror circuit board assembly isshown. It is envisioned that either a single sided or two sided,conventional circuit board may be employed. Rearview mirror housing 850encloses circuit board 860, carrying forward ambient light sensor 58,glare sensor 62, and skyward ambient light sensors 150, 150′, 158, 158′on surface 861 of the board 860. Glare sensor 62 may be bent aroundcircuit board 860 or may be connected to circuit board 860 by flexiblewires to permit glare sensor 62 to view glare 34 from generally behindvehicle 20. Alternatively, if a two sided circuit board is used, theglare sensor 62 may be mounted to the front of the circuit board.Moisture sensor 120 may include emitter 104 and one or more lightsensors 110, 110 a connected to circuit board 860 by cabling 862.Circuit board 860 may include control logic 66 receiving sensor signalsand generating equipment control signals responsive thereto. Cable 863supplies power and ground to circuit board 860 as well as carryingequipment control signals from circuit board 860 to the remainder of thevehicle electrical system. The cable 863 may be mounted to the circuitboard via a conventional multi-pin connector 865.

An automatic vehicle equipment control circuit 165 is illustrated inblock diagram form in FIG. 4, a portion of which is mounted in interiorrearview mirror 24. The control circuit 165 includes an ambient lightsensor 150, an optional ambient light sensor 158, an optional ambientlight sensor 150′, and optional ambient light sensor 158′, a glaresensor 62, a forward ambient light sensor 58, a moisture sensor 110, anoptional moisture sensor 110 a, and an emitter 104 connected to controllogic 66 through busses 164. It will be recognized that fewer sensorscould be provided. Additional sensors, such as other light sensors,speed sensors and temperature sensors that are not illustrated, may alsobe connected to the control logic 66. Busses 164 connect each of thelight sensors and the emitter to control logic 66. Control logic 66 maybe responsive to light signals on busses 164 to generate equipmentcontrol signals on busses 166 so as to control various automotivevehicle equipment such as headlamps 44, wipers 38, a defogger 40, adefroster 42, and rearview mirrors 24, 26 automatically. Less oradditional equipment could be controlled by the control logic 66. Lightlevel signals on busses 164 and control signals on busses 166 may beanalog, discrete, digital, or the like, to fit the particular need ofthe sensors and equipment. Although shown as a single box that can belocated in the mirror housing 850, it will be recognized that thecontrol logic 66 may be distributed throughout vehicle 20. It will berecognized that significant cost and manufacturing advantages can beachieved by implementing the control logic using a minimum number ofcomponents. Equipment control signal as used herein refers to a signalthat is used in controlling equipment, which control signal can be useddirectly by the equipment or input to further circuitry which controlsthe equipment.

Somewhat more particularly, one or more of the light sensors 58, 62,110, 110 a, 150, 150′, 158, 158′ are implemented using a light sensorthat incorporates a silicon-based light transducer and conditioningelectronics, which is advantageously implemented on a single substrate.The light transducer generates charge at a rate proportional to theamount of incident light. This light-induced charge is collected over anintegration period. The resulting potential on bus 164 is proportionalto, and thus indicative of, the level of light to which the sensor isexposed over the integration period. Such a light sensor with integralcharge collection has many advantages. For example, the ability toincorporate additional electronics on the same substrate as thetransducer increases noise immunity and permits the sensor output to beformatted for use by a digital circuit. Component integrationadditionally reduces the system cost. Silicon devices are moretemperature invariant than CdS cells and can be packaged to provideprotection from humidity, shock, and vibration. Additionally,silicon-based light sensors have a faster response time than CdS cells,speeding up the response time of the automatic equipment. Onedisadvantage of silicon-based light transducers is that they have afrequency response substantially different than that of the human eye.Types of charge accumulating light transducers include photodiodes andphotogate transistors. A variety of charge integrating photodiodedevices are known, including those in U.S. Pat. No. 4,916,307 to Nishibeet al.; U.S. Pat. No. 5,214,274 to Yang; U.S. Pat. No. 5,243,215 toEnomoto et al.; U.S. Pat. No. 5,338,691 to Enomoto et al.; and U.S. Pat.No. 5,789,737 to Street. Photogate transistor devices are described inU.S. Pat. No. 5,386,128 to Fossum et al. and U.S. Pat. No. 5,471,515 toFossum et al.

The control logic 66 includes a controller that can advantageously beimplemented using a microprocessor, microcontroller, digital signalprocessor, programmable logic unit, or the like. A PIC 16C620Amicrocontroller commercially available from Microchip may be used. Thecontrol logic receives light signals from sensors 58, 62, 110, 110 a,150, 150′, 158, 158′ responsive to which it determines alight level. Themicrocontroller need not include an analog-to-digital converter (ADC)connected to receive the output from the sensors 58, 62, 110, 110 a,150, 150′, 158, 158′ if these sensors produces discrete, digitaloutputs. The microcontroller may optionally include electronicallyalterable memory in which calibrated thresholds associated with each ofthe sensors are stored during manufacture of the mirror 24 for later usein controlling equipment 24, 26, 38, 40, 42 and 44 in a predeterminedmanner. The microcontroller in control logic 66 preferably generatescontrol signals on lines 164 that select the sensitivity of the sensors58, 62, 110, 110 a, 150, 150′, 158, 158′ to effect a wide dynamic rangefor the light sensors. The microcontroller also generates controlsignals applied to the automatically controlled equipment 24, 26, 38,40, 42, and 44 responsive at least in part to the signals from thesensors.

Referring now to FIG. 5, the control logic 66 and sensors 58, 62, 110,110 a, 150, 150′, 158, 158′ will be described in greater detail. Lightsensor 170 refers generally to a light sensor that can be used toimplement any of the sensors 58, 62, 110, 110 a, 150, 150′, 158, 158′.The control logic 66 and light sensor 170 are interconnected by a singleline 164 that carries interconnect signals 186, which can advantageouslyinclude both light sensor sensitivity control signals and resultantlight sensor output signals. The microcontroller used to implementcontrol logic 66 includes a transistor element Q1 and a buffer 192connected to an output pin 188, or other input/output (I/O) pinstructure, which is connected to signal line 164. The transistor elementQ1 may be implemented using a suitable transistor such as a field effecttransistor (FET), connected between signal pin 188 and ground.Transistor Q1 is controlled by control line 190 connected to the base oftransistor Q1. Buffer 192 is also connected to signal pin 188 to isolatethe signal line 164 from signal levels present in the microcontroller.

Light sensor 170 includes enclosure 172 with window 174 admitting light176 incident on exposed light transducer 178. Enclosure 172 admits powerpin 180, ground pin 182, and signal pin 184. “Window” as used hereinrefers to a path by which light travels through the sensor package toreach the transducer surface, and thus could be an opening in an opaquesemiconductor package, a transparent or translucent encapsulant, or thelike. The use of only three pins 180, 182, 184 greatly reduces the costof light sensor 170 and associated control logic 66.

Light sensor 170 is connected to control logic 66 through bus 164, whichcarries interconnection signal 186 between signal pin 184 in lightsensor 170 and signal pin 188 in control logic 66. As will be describedbelow, signal pins 184, 188 are tri-state ports permitting interconnectsignal 186 to provide both an input to light sensor 170 and an outputfrom light sensor 170.

Within light sensor 170, transistor Q2, which can be implemented using asuitable transistor such as a FET element, is connected between signalpin 184 and ground. Transistor Q2 is controlled by output pulse 194connected to the gate of Q2. Constant current source 196 is connected tosignal pin 184 so that if neither transistor Q1 nor transistor Q2 are ON(high logic level), interconnect signal 186 is pulled to a high logiclevel. Constant current source 196 nominally sources about 0.5 mA topull up interconnect signal 186. The input of Schmidt trigger inverter198 is connected to signal pin 184. Inverters 200 and 202, which areconnected in series, follow Schmidt trigger inverter 198. The output ofinverter 202 clocks D flip-flop 204. The output of multiplexer 206 isconnected to the D input of flip-flop 204. The select input ofmultiplexer 206 is driven by output pulse 194 such that when outputpulse 194 is asserted, the D input of flip-flop 204 is unasserted, andwhen output pulse 194 is not asserted the D input of flip-flop 204 isasserted. The output of NAND gate 208 is connected to low assertingreset 210 of flip-flop 204. The output of flip-flop 204 is integrationpulse 212. Integration pulse 212 and the output of inverter 200 areinputs to NAND gate 208. Light-to-pulse circuit 214 accepts integrationpulse 212 and the output of exposed light transducer 178 and producesoutput pulse 194.

Light sensor 170 may advantageously include a shielded light transducer216, which does not receive light 176. Shielded light transducer 216 hassubstantially the same construction as exposed light transducer 178,being of the same size and material as transducer 178. Light-to-pulsecircuit 214 uses the output of shielded light transducer 216 to reducethe affects of noise in exposed light transducer 178.

Referring now to FIG. 6, a timing diagram illustrating operation of thecircuitry of FIG. 5 is shown. Initially, low asserting interconnectsignal 186 is high. The state of flip-flop 204 must be zero for, if thestate is one, both inputs to NAND gate 208 would be high, assertingreset 210 and forcing the state of flip-flop 204 to zero.

At time 220, control logic 66 asserts control line 190 turningtransistor Q1 ON. Interconnect signal 186 is then pulled low at time222. The output of inverter 202 transitions from low to high setting thestate of flip-flop 204 to one (i.e., a high logic level) which causesintegration pulse 212 to become asserted at time 224. Light-to-pulsecircuit 214 begins integrating light 176 incident on exposed lighttransducer 178. At time 226, control line 190 is brought low turningtransistor Q1 off. The difference between time 226 and time 220 isintegration period 228 requested by control logic 66. Since bothtransistors Q1 and Q2 are off, interconnect signal 186 is pulled high bycurrent source 196 at time 230. Since the output of inverter 200 andintegration pulse 212 are both high, reset 210 is asserted causing thestate of flip-flop 204 to change to zero and integration pulse 212 tobecome unasserted at time 232. This signals light-to-pulse circuit 214to stop integrating light 176 incident on exposed light transducer 178.

At time 234, light-to-pulse circuit 214 asserts output pulse 194 tobegin outputting light intensity information. Asserting output pulse 194turns transistor Q2 on, pulling interconnect signal 186 low at time 236.This causes inverter 202 to output a low-to-high transition clocking azero as the state of flip-flop 204. Light-to-pulse circuit 214 deassertsoutput pulse 194 at time 238. The difference between time 238 and time234 is light intensity period 240 indicating the amount of light 176incident on exposed light transducer 178 over integration period 228.Transistor Q2 is turned off when output pulse 194 goes low at time 238.Since both transistors Q1 and Q2 are off, interconnect signal 186 ispulled high at time 242. Buffer 192 in control logic 66 detects thetransitions in interconnect signal 186 at times 236 and 242. Thedifference in time between times 242 and 236 is used by control logic 66to determine the intensity of light 176 received by light sensor 170.

If shielded light transducer 216 is included in light sensor 170, thedifference in time between the deassertion of integration pulse 212 attime 232 and the assertion of output pulse 194 at time 234 is due, inpart, to the thermal noise in light sensor 170. This difference isexpressed as thermal noise period 244. Thermal noise period 244 may beused by control logic 66 to determine the temperature of light sensor170 or may be more simply used to determine when the noise level insensor 170 is too high for a reliable reading. Control logic 66 maydisable automatic control of vehicle equipment if the temperature oflight sensor 170 exceeds a preset limit.

FIG. 7 illustrates a timing diagram of integration duration control andsensor output for a light sensor. Charge accumulating light sensor 170exhibits increased sensitivity and increased dynamic range throughvariable integration periods. The total amount of light-induced charge,which can be effectively measured, is limited. Therefore, in thepresence of bright light, a short integration time is desirable toprevent saturation. However, if a short integration time is used in lowlight conditions, the charge signal may be lost in noise inherent insensor 170 (i.e., the signal-to-noise ratio will be so low that thesignal level will be undetectable).

Control line 190 includes a sequence of integration periods havingvarying lengths. In the example shown, short integration pulse 240having short integration period 242 is generated. A semiconductor lightsensor may output a short pulse in a completely dark environment due tonoise. Therefore, any sensor output pulse 194, such as short signalpulse 244, having a duration less than a threshold is ignored by controllogic 66. Next, medium integration pulse 246 having medium integrationperiod 248 is generated. Resulting medium signal pulse 250 has aduration indicative of the amount of light incident on sensor 170 duringmedium integration period 248. Long integration pulse 252 having longintegration period 254 is generated. If light sensor 170 is sufficientlybright, saturation will result. Therefore, long signal pulse 256 havinga duration greater than a threshold is also ignored by control logic 66.The signal represented by control line 190 may be generated outside oflight sensor 170, such as by control logic 66, or may be generated bysensor logic within light sensor 170. By varying the integration period,the sensitivity is adjusted. Varying the sensitivity by providingsuccessive integration periods of different duration allows theappropriate sensitivity to be detected, and responsive thereto,selected. A significant advantage of the sensor having bi-directionalinterconnect signal 186 is that the control logic 66 can control thesensitivity of the sensor 170 to dynamically compensate for differentlight conditions by varying the integration periods for the sensor.

Referring now to FIG. 8, a schematic diagram illustrating operation of alight sensor having a pulse output is shown. Light-to-pulse circuit 300includes exposed light transducer 178 for converting light 176 incidenton exposed light transducer 178 into charge accumulated in light storagecapacitor 304, indicated by C_(SL). Exposed light transducer 178 may beany device capable of converting light 176 into charge, such as thephotogate sensor described in U.S. Pat. No. 5,471,515 titled “ActivePixel Sensor With Intra-Pixel Charge Transfer” to E. Fossum et al.Preferably, light transducer 178 is a photodiode such as is describedbelow. Except as noted, the following discussion does not depend on aparticular type or construction for exposed light transducer 178.

Light-to-pulse circuit 300 also includes light-to-pulse circuit 214(FIG. 8) which is connected to transducer 178, receives an integrationpulse 212, and outputs a light comparator signal which is proportionalto the amount of light 176 impacting transducer 178 during integrationperiod pulse 212. Light to pulse circuit 214 operates under the controlof sensor logic 306. Sensor logic 306 generates reset signal 308controlling switch 310 connected between exposed light transducer output312 and V_(DD). Sensor logic 306 also produces sample signal 314controlling switch 316 between exposed light transducer output 312 andlight storage capacitor 304. The voltage across light storage capacitor304, light storage capacitor voltage 318, is fed into one input ofcomparator 320. The other input of comparator 320 is ramp voltage 322across ramp capacitor 324. Ramp capacitor 324 is in parallel withcurrent source 326 generating current I_(R). Sensor logic 306 furtherproduces ramp control signal 328 controlling switch 330 connectedbetween ramp voltage 322 and V_(DD). Comparator 320 produces comparatoroutput 332 based on the relative levels of light storage capacitorvoltage 318 and ramp voltage 322. Sensor logic 306 may generate resetsignal 308, sample signal 314, and ramp control signal 330 based oninternally generated timing or on externally generated integration pulse212.

Referring now to FIG. 9, a timing diagram illustrating operation of thelight sensor of FIG. 8 is shown. A measurement cycle is started at time340 when sample signal 314 is asserted while reset signal 308 isasserted. This closes switch 316 to charge light storage capacitor 304to V_(DD) as indicated by voltage level 342 in light storage capacitorvoltage 318. Reset signal 308 is then deasserted at time 344, openingswitch 310 and beginning integration period 346. During integrationperiod 346, light 176 incident on exposed light transducer 178 generatesnegative charge causing declining voltage 348 in light storage capacitorvoltage 318. At time 350, ramp control signal 328 is asserted closingswitch 330 and charging ramp capacitor 324 so that ramp voltage 322 isV_(DD) as indicated by voltage level 352.

Sample signal 314 is deasserted at time 354, causing switch 316 to open,thereby ending integration period 346. At some time 356 following time354 and prior to the next measurement cycle, reset signal 308 must beasserted closing switch 310. At time 358, ramp control signal 328 isdeasserted opening switch 330. This causes ramp capacitor 324 todischarge at a constant rate through current source 326 as indicated bydeclining voltage 360 in ramp voltage 322. Initially, as indicated byvoltage level 362, comparator output 332 is unasserted because rampvoltage 322 is greater than light storage capacitor voltage 318. At time364, declining voltage 360 in ramp voltage 322 drops below light storagecapacitor voltage 318 causing comparator output 332 to become asserted.Comparator output 322 remains asserted until time 366 when ramp controlsignal 328 is asserted closing switch 330 and pulling ramp voltage 322to V_(DD). The difference between time 366 and time 364, indicated bypulse duration 368, is inversely related to the amount of light 176received by exposed light transducer 178 during integration period 346.The integration period 346 can be set directly by the integration pulse212, or a signal derived from integration pulse 212. It is envisionedthat the integration period 346 will be proportional to the width of theintegration pulse 212, which is proportional to the pulse width of thecontrol line signal 190, in the circuit of FIG. 5.

Referring now to FIG. 10, a schematic diagram illustrating operation ofa light sensor with noise compensation is shown. A light-to-pulsecircuit, shown generally by 380, improves upon light-to-pulse circuit300 by incorporating shielded light transducer 216 and associatedelectronics. Shielded light transducer 216 preferably has the sameconstruction as exposed light transducer 178. However, shielded lighttransducer 216 does not receive light 176. Charge generated by shieldedlight transducer 216, therefore, is only a function of noise. This noiseis predominately thermal in nature. By providing shielded lighttransducer 216 having the same construction as exposed light transducer178, such that the exposed and shielded transducers have the samesurface area and material composition, and may be deposited on the samedie, the noise signal produced by shielded light transducer 216 willclosely approximate the noise within the signal produced by exposedlight transducer 178. By subtracting the signal produced by shieldedlight transducer 216 from the signal produced by exposed lighttransducer 178, the effect of noise in light transducer 178 can begreatly reduced.

Reset signal 308 controls switch 382 connected between shieldedtransducer output 384 and V_(DD). Sample signal 314 controls switch 386connected between shielded transducer output 384 and noise storagecapacitor 388, indicated by C_(SN). The noise storage capacitor voltage390, which is the voltage across noise storage capacitor 388, is oneinput to comparator 392. The second input to comparator 392 is rampvoltage 322. The outputs of comparator 392, noise comparator output 394,and comparator output 332, serve as inputs to exclusive-OR gate 396.Exclusive-OR gate 396 generates exclusive-OR output 398 indicating theintensity of light 176.

Referring now to FIG. 11, a timing diagram illustrating operation of thelight sensor of FIG. 10 is shown. Light-to-pulse circuit 380 functionsin the same manner as light-to-pulse circuit 300 with regard to resetsignal 308, sample signal 314, light storage capacitor voltage 318, rampvoltage 322, ramp control signal 328, and comparator output 332. At time340, sample signal 314 is asserted while reset signal 308 is asserted.Switches 382 and 386 are both closed charging noise storage capacitor388 to V_(DD) as indicated by voltage level 410 in noise storagecapacitor voltage 390. At time 344, reset signal 308 is deassertedopening switch 382 and causing declining voltage 412 in noise storagecapacitor voltage 390 from charge produced by shielded light transducer216 due to noise. At time 354, sample signal 314 is deasserted endingintegration period 346 for noise collection. At time 358, ramp controlsignal 328 is deasserted causing declining voltage 360 in ramp voltage322. Initially, as indicated by voltage level 414, noise comparatoroutput 394 is unasserted because ramp voltage 322 is greater than noisestorage capacitor voltage 390. Since comparator output 332 is alsounasserted, output 398 from comparator 396 is unasserted as indicated byvoltage level 416. At time 418, ramp voltage 322 drops below the levelof noise storage capacitor voltage 390, causing noise comparator output394 to become asserted. Since noise comparator output 394 and comparatoroutput 332 are different, output 398 from comparator 396 is asserted. Attime 364, ramp voltage 322 drops beneath the level of light storagecapacitor voltage 318, causing comparator output 332 to become asserted.Since both noise comparator output 394 and comparator output 332 are nowasserted, output 398 from exclusive-OR gate 396 now becomes unasserted.The difference between time 364 and time 418, output pulse duration 420,has a time period proportional to the intensity of light 176 incident onexposed light transducer 178 less noise produced by shielded lighttransducer 216 over integration period 346. The duration between time418 and time 358, noise duration 422, is directly proportional to theamount of noise developed by shielded light transducer 216 overintegration period 346. Since the majority of this noise is thermalnoise, noise duration 422 is indicative of the temperature of shieldedlight transducer 216. At time 366, ramp control signal 328 is asserted,deasserting both noise comparator output 394 and comparator output 332.

Referring now to FIG. 12, a schematic diagram of an implementation ofthe light sensor of FIG. 10 using photodiodes as light transducers isshown. Light-to-pulse circuit 380 is implemented using exposedphotodiode 430 for exposed light transducer 178 and shielded photodiode432 for shielded light transducer 216. The anode of exposed photodiode430 is connected to ground and the cathode connected through transistorQ20 to V_(DD). The base of transistor Q20 is controlled by reset signal308. Hence, transistor Q20 functions as switch 310. Transistors Q21 andQ22 are connected in series between V_(DD) and ground to form a buffer,shown generally by 434. The base of transistor Q21 is connected to thecollector of exposed photodiode 430. The base of load transistor Q22 isconnected to fixed voltage V_(B). The output of buffer 434 is connectedthrough transistor Q23 to light storage capacitor 304. The base oftransistor Q23 is driven by sample signal 314, permitting transistor Q23to function as switch 316. The anode of shielded photodiode 432 isconnected to ground and the cathode is connected to V_(DD) throughtransistor Q24. The base of transistor Q24 is driven by reset signal 308permitting transistor Q24 to function as switch 382. Transistors Q25 andQ26 form a buffer, shown generally by 436, isolating the output fromshielded photodiode 432 in the same manner that buffer 434 isolatesexposed photodiode 430. Transistor Q27 connects the output of buffer 436to noise storage capacitor 388. The base of transistor Q27 is driven bysample signal 314 permitting transistor Q27 to function as switch 386.Typically, light storage capacitor 304 and noise storage capacitor 388are 2 pF. Ramp capacitor 324, typically 10 pF, is charged to V_(DD)through transistor Q28. The base of transistor Q28 is driven by rampcontrol signal 328 permitting transistor Q28 to function as switch 330.Ramp capacitor 324 is discharged through current source 326 at anapproximately constant current I_(R) of 0.01 μA when transistor Q28 isoff.

Sensor power-up response is improved, and the effective dynamic range ofthe sensor is extended, by including circuitry to inhibit output if rampvoltage 322 drops beneath a preset voltage. Light-to-pulse circuit 380includes comparator 438 comparing ramp voltage 322 with initializationvoltage (V_(INIT)) 440. Comparator output 442 is ANDed with exclusive-ORoutput 396 by AND gate 444 to produce AND gate output 446. Duringoperation, if ramp voltage 322 is less than initialization voltage 440,output 446 is deasserted (i.e., is held to a low logic level). The useof comparator 438 and AND gate 444 guarantee that output 446 is notasserted regardless of the state of light-to-pulse circuit 380 followingpower-up. In a preferred embodiment, the initialization voltage is 0.45V.

Sensor logic 306 generates control signals 308, 314, 328 based onintegration pulse 212 which may be generated internally or provided froman external source. Buffer 447 receives integration pulse 212 andproduces sample control 314. An odd number of sequentially connectedinverters, shown generally as inverter train 448, accepts sample control314 and produces reset control 308. A second set of odd numberedsequentially connected inverters, shown generally as inverter train 449,accepts reset signal 308 and produces ramp control signal 328. Thecircuit shown in FIG. 12 has a resolution of at least 8 bits and asensitivity of approximately 1 volt per lux-second. The maximum outputpulse duration 420 is independent of integration period 346 provided bythe duration of integration pulse 212.

It is envisioned that the light signal 318 across capacitor 304 in FIG.12 and the noise signal 390 across capacitor 388 may be input todifferential operational amplifier 321 (FIG. 12a). The output ofdifferential amplifier 321 is an analog signal representative of thedifference between the light signal 318 and the noise signal 390. Thiscircuit can be used where the control logic 66 includes ananalog-to-digital converter that can convert these digital signals toanalog signals.

Referring now to FIGS. 13-16, various embodiments for light sensorpackaging, output, and control are shown. Each embodiment may includelight-to-pulse circuitry as described above. In FIG. 13, light sensorpackage 450 accepts four pins for supply voltage V_(DD), ground,sensitivity control signal 452, and output signal 454. Sensitivitycontrol signal 452 may be integration pulse 212 used by light-to-pulsecircuit 380 to produce output 398, which is sent as output signal 454.In FIG. 14, light sensor package 456 requires only three pins forV_(DD), ground, and combined sensitivity control and output signal 458.Combined signal 458 may be interconnect signal 186 as described above.In FIG. 15, light sensor package 460 admits three pins for output signal454, ground, and combined V_(DD) and sensitivity control signal 462. Asis known in the art, combined signal 462 may be separated into powersupply voltage V_(DD) and sensitivity control signal 452 through the useof filters. For example, a low-pass and high-pass filter can be used toseparate the signals. In FIG. 16, light sensor package 464 admits threepins for V_(DD), ground, and output signal 454. Sensitivity controlsignal 452 is generated within light sensor package 464 as describedbelow.

Referring now to FIG. 17, a block diagram of sensor logic fordetermining the integration period signal within sensor 170 is shown.Sensor logic 306 may include free-running counter 470 driven by internaloscillator 472. Counter 470 may have taps, one of which is indicated by474, connected to different counter bits. For example, one tap 474 maybe connected to the n^(th) bit, the next tap 474 to the n^(th)+2 bit,the next tap 474 connected to the n^(th)+4 bit, and so on, with eachsuccessive tap thereby providing a pulse with a period four times longerthan the preceding tap 474. Sensor control signal generator 476 controlsswitch 478 to determine which tap 474 will be used to produceintegration pulse 212. Typically, sensor control signal generator 476sequences through each tap 474 repeatedly. Sensor control signalgenerator 476 then uses integration pulse 212 to generate controlsignals such as reset signal 308, sample signal 314, and ramp controlsignal 328 as described above. It will be recognized that where thesensor generates the integration pulse internally to vary the sensorsensitivity, although the control logic will be unable to alter theintegration period, the control logic will receive short, intermediateand long output pulses from the sensor responsive to which measuredlight levels can be determined bright, intermediate and low lightlevels.

Referring now to FIG. 18, an alternate embodiment of the light sensor isillustrated wherein light transducers having different effective areasare used to achieve variable sensitivity. As an alternative to varyingthe integration time, or together with varying the integration time,pairs of exposed light transducer 178 and shielded light transducer 216having different effective areas may be used. If photodiodes 430, 432are used as light transducers 178, 216, the effective area is thephotodiode collector area. Small exposed light transducer 490 producescharge, which is converted to a voltage by light-to-voltage circuit 492.Light-to-voltage circuit 492 may be implemented using switches 310, 316,and light storage capacitor 304 as described above. Charge produced bysmall shielded light transducer 494 is converted to voltage bynoise-to-voltage circuit 496. Noise-to-voltage circuit 496 may beimplemented using switches 382, 386 and noise storage capacitor 388 asdescribed above. The outputs of light-to-voltage circuit 492 andnoise-to-voltage circuit 496 are converted to a pulse byvoltage-to-pulse circuit 498, with a width based on charge accumulatedover an integration period by small exposed light transducer 490 lesscharge due to noise integrated by small shielded light transducer 494.Voltage-to-pulse circuit 498 may be implemented using comparators 320,392, capacitor 324, current source 326, and gate 396 as described above.Medium exposed light transducer 500 has an effective area larger thanthe effective area for small exposed light transducer 490, resulting inincreased sensitivity. For example, if the effective area of mediumexposed light transducer 500 is four times larger than the effectivearea of small exposed light transducer 490, medium exposed lighttransducer 500 will be four times more sensitive to light 176 than willbe small exposed light transducer 490. Medium shielded light transducer502 has an effective area the same as medium exposed light transducer500. Additional light-to-voltage circuit 492, noise-to-voltage circuit496, and voltage-to-pulse circuit 498 produce a noise-corrected outputpulse with a width based on light 176 incident on medium exposed lighttransducer 500 over the integration period. Similarly, large exposedlight transducer 504 and large shielded light transducer 506 providestill increased sensitivity over medium exposed light transducer 500 andmedium shielded light transducer 502 by having still greater effectivearea.

Switch 508 under the control of sensor logic 306 sets which output fromvoltage-to-pulse circuits 498 will be used for output signal 454. Outputsignal 454 may be selected based on a signal generated within sensorlogic 306 or may be based on a signal provided from outside of sensorlogic 306. In particular, a control signal may be provided by controllogic 66 that controls switch 908 to select one of the small, medium andlarge light transducers for connection to output 454.

In an alternative embodiment, only one shielded light transducer 216 isused. The output of shielded light transducer 216 is scaled prior toeach noise-to-voltage circuit 496 in proportion to the varying effectiveareas of exposed light transducers 178. It will be recognized by one ofordinary skill in the art that, though the examples shown in FIG. 22have three pairs of exposed light transducers 178 and shielded lighttransducers 216, any number of pairs may be used.

Referring now to FIG. 19, a block diagram illustrating the use of lighttransducers having different apertures to achieve increased dynamicrange is shown. As an alternative to or together with specifying theintegration period, exposed light transducers 178 having the sameeffective area may each have a different aperture admitting area foradmitting light 176. Varying apertures may be produced using partialshield 520 blocking light 176 from reaching a portion of exposed lighttransducer 178. Each exposed light transducer 178 produces chargeconverted to a voltage by a corresponding light-to-voltage circuit 492.Switch 522 under the control of sensor logic 306 selects whichlight-to-voltage circuit's 492 output is connected to voltage-to-pulsecircuit 498. Voltage-to-pulse circuit 498 produces output signal 454compensated for noise sensed by shielded light transducer 216 andprocessed by noise-to-voltage circuit 496. Sensor logic 306 may selectoutput of light-to-voltage circuits 492 based on an internally generatedcontrol signal or on a control signal received from control logic 66.

In light sensor 170 with multiple transducers 178, 490, 500, 504, lightsensor 170 detects incident light within a target spatial distribution.Each transducer 178, 490, 500, 504 views the same target spatialdistribution. Hence, control logic 66 generates at least one equipmentcontrol signal 166 based on light signal 164 without mapping lightsignal 164 to an area within the target spatial distribution.

Referring now to FIG. 20, a transducer that can be used to achievevariable sensitivity is shown. A photodiode, shown generally by 530, isformed by n-type diffusion 532 in p-type substrate 534. Light 176incident on photodiode 530 generates charge 536 which may be accumulatedin photodiode well 538 beneath n-type diffusion 532. Photodiode 530 hasintrinsic photodiode capacitance C_(PD). Floating diffusion 540 is alsoformed by diffusing n-type material in substrate 534. Floating diffusion540 is connected through transistor Q20 to reset voltage V_(RESET). Thegate of transistor Q20 is connected to reset signal 308 under thecontrol of sensor logic 306. Floating diffusion 540 is also connected tothe input of buffer 542. The output of buffer 542 is transducer outputV_(OUT). Floating diffusion 540 defines diffusion well 544 formed in aregion of substrate 534 when reset signal 308 is asserted. Floatingdiffusion 540 has an intrinsic floating diffusion capacitance C_(FD).Transmission gate 546 is positioned between diffusion 532 and floatingdiffusion 540. Transmission gate 546 is held at voltage V_(TG) to formtransmission well 548 thereunder. Transmission well 548 has a depthshallower than photodiode well 538 and diffusion well 544. Transmissiongate 546 has an intrinsic transmission gate capacitance C_(TG).

When reset signal 308 is asserted, bringing floating diffusion 540 toV_(RESET), charge is eliminated in diffusion well 544. Further, whencharge is reset in diffusion well 544, any charge 536 in photodiode well538 above the depth of transmission well 548 flows through transmissionwell 548, through floating diffusion 540, and is eliminated. During alight integration period, reset signal 308 is unasserted, causing thevoltage of floating diffusion 540 to float based on the amount of charge536 in diffusion well 544. As light 176 strikes diffusion 532, charge536 is created. Since charge 536 in photodiode well 538 up to the levelof transmission well 548 was not eliminated by charge reset, additionalcharge 536 produced by incident light 176 flows from photodiode well 538through transmission well 548 and into diffusion well 544. At chargelevel 550, beneath the level of transmission well 548, only diffusionwell 544 is filling with charge 536. Hence, the voltage of floatingdiffusion 540 is inversely proportional to floating gate capacitanceC_(FD). When enough charge 536 has been generated to fill diffusion well544 above the level of transmission well 548 such as, for example level552, diffusion well 544, transmission well 548, and photodiode well 538all fill with charge 536. Hence, the voltage of floating diffusion 540is now inversely proportional to the sum of floating diffusioncapacitance C_(FD), transmission gate capacitance C_(TG), and photodiodecapacitance C_(PD). The result is light sensor 170 with a sensitivitydetermined from the magnitude of the resulting light signal.

Referring now to FIG. 21, a graph of output potential as a function ofaccumulated incident light for the transducer of FIG. 20 is shown. Acurve, shown generally by 554, shows transducer output V_(OUT) as afunction of light 176 incident on diffusion 532 and, possibly, floatingdiffusion 540 over the integration period. During steep portion 556,charge 536 is accumulating in diffusion well 544 alone. Since theconversion gain is based only on floating diffusion capacitance C_(FD),photodiode 530 appears to have a high sensitivity to incident light 176.During shallow portion 558, charge 536 is accumulated in diffusion well544, transmission well 548, and photodiode well 538. Since theconversion gain is now dependent on the parallel combination ofcapacitances C_(FD), C_(TG), and C_(PD), photodiode 530 now appears lesssensitive to incident light 176. By adjusting voltages V_(RESET) andV_(TG), knee point 559 between steep portion 556 and shallow portion 558can be shifted affecting the dynamic range. For example, if the maximumvoltage swing for floating diffusion 540 is 1 volt; the ratio of C_(FD)to the sum of C_(FD), C_(TG), and C_(PD) is 1:100; and knee point 559 isset at 0.5 volts, the dynamic range of photodiode 530 is increased about50 times over the dynamic range of a similar photodiode without dualcapacitance.

Referring now to FIG. 22, a schematic diagram illustrating a photodiodetransducer incorporating an anti-bloom gate is shown. Anti-bloom gate560 is formed between diffusion 532 and source voltage diffusion 562tied to V_(DD). Anti-bloom gate 560 is tied to anti-bloom voltageV_(AB). Anti-bloom gate 560 forms anti-bloom well 564 in substrate 534between photodiode well 538 and source diffusion well 566. Anti-bloomvoltage V_(AB) is less than transmission gate voltage V_(TG) well 564,making anti-bloom well 564 shallower than transmission well 548. Whenaccumulated charge generated by photodiode 530 exceeds charge level 568equal to the depth of anti-bloom well 564, the excess charge flowsbeneath anti-bloom gate 560 into source voltage diffusion 562 and iseliminated. Anti-bloom gate 560 prevents output voltage V_(OUT) fromdropping below a level detectable by comparator 320 in light-to-pulsecircuit 380.

Referring now to FIG. 23, a drawing illustrating enclosure for a lightsensor is shown. Light sensor 170 includes enclosure 172 having window174 for admitting light, one ray of which is indicated by 570. Enclosure172 admits power pin 180, ground pin 182, and signal pin 184.Semiconductor die 572, encapsulated within enclosure 172, incorporateslight transducers 178, 216 and associated electronics as describedabove. Pins 180, 182, 184 may be wire bonded to die 527, as shown bywire 574 for power pin 180 and wire 576 for signal pin 184, or may bedirectly bonded to die 527, as shown for ground pin 182.

Enclosure 172 may be the same type used to construct three-terminallight emitting diodes (LEDs). A preferred format is commonly referred toas the T-1¾ or 5 mm package. Encapsulating electronics in such packagesis well known in the art of optical electronics manufacturing.

A lens, shown generally by 578, is preferably used to focus light ontoexposed light transducer 178. Lens 578 may be provided by a separatediscrete lens positioned between light sensor 170 and the source oflight rays 570, or the lens may be integral with the encapsulant 172 asshown in FIG. 27. In either case, lens 578 defines the field of view oflight sensor 170 and provides improved sensitivity through optical gain.The lens can define the sensor field to have a narrow or wide angle.

Referring now to FIG. 24, a graph illustrating the light sensor field ofview as a function of light transducer distance from the lens is shown.The field of view for exposed light transducer 178 in light sensor 170is defined as view angle θ made by marginal ray 570 with respect tooptical axis 580 through exposed light transducer 178. The half-anglefield of view for spherical lens 578 is expressed by Equation 1:

θ=90−arccos{r/R}+n₂/n₁*sin{arcos{r/R}−arctan{(d−(R²−r²)^(½)))/r}}

where r is the lens aperture radius, R is the radius of curvature oflens 578, n₂ is the index of refraction of material within enclosure172, n₁ is the index of refraction outside of enclosure 172, d is thedistance from the center of lens 578 to exposed light transducer 178,and θ is measured in degrees. Typically, T-1¾ enclosure 172 is filledwith epoxy and sensor 170 operates in air making the ratio of n₂ to n₁approximately 1.5. Curve 590 plots half angle field of view θ as afunction of distance d for a T-1¾ enclosure having a spherical lens 578with radius R of 5.0 mm. As light transducer 178 moves farther from lens578, the field of view decreases.

Referring now to FIG. 25, a graph illustrating light sensor optical gainas a function of light transducer distance from the lens is shown.Assuming paraxial approximation for rays 570, the optical gain of lens578 can be estimated by considering the ratio of additional opticalenergy collected by light transducer 178 with lens 578 to the opticalenergy collected by light transducer 178 without lens 578. This can becomputed by considering a cone of light with a base at the surface oflens 578 and a point at the focal point f of lens 578. The optical gainG may then be expressed as a function of the ratio of the cross sectionof the cone to the area of light transducer 178 which reduces toEquation 2:

G=f²/(f−d)²

Curve 600 shows optical gain G as a function of distance d for a T-1¾enclosure having a spherical lens 578 with radius R of 5.0 mm and afocal length f of 15.0 mm. As light transducer 178 moves farther fromlens 578, the optical gain increases.

For use in automatically dimming rearview mirrors, the distance dbetween lens 578 and light transducer 178 can be adjusted for optimalperformance of forward ambient light sensor 58 and glare sensor 62.Forward ambient light sensor 58 should have a wide field of view butneed not be as sensitive as glare sensor 62. Glare sensor 62 should havea narrower field of view but must be more sensitive and, therefore,benefits from a higher optical gain. For the lens described above, adistance d of between 2 mm and 3 mm is suitable for forward ambientlight sensor 58 and a distance d of between 6 mm and 7 mm is suitablefor glare sensor 62. In addition to modifying lens parameters, otherlens types such as aspheric, cylindrical, and the like are possiblewithin the spirit and scope of the present invention.

Referring now to FIG. 26, an alternate light sensor 170′ having analternate encapsulant shape is illustrated. Light sensor 170′ hasenclosure 172 with curved surface 174 formed as an asymmetricalcylindrical lens, shown generally by 604. Lens 604 may have any desiredradius and length, and may for example have a radius r (FIG. 30a) of1.25 mm and a length of 5 mm. When mounted in the vehicle with thelongitudinal axis of the cylindrical lens 604 generally normal with thehorizon, horizontal compression without corresponding verticalcompression is achieved. This permits observance of a wide region of thesky without sensing a correspondingly wide region of the ground, thevehicle roof, or the vehicle hood, when the sensor is used for the skysensor. Conversely, when mounted horizontally, a wide horizontal viewinput is achieved. This characteristic can be advantageously used toimplement the glare sensor, as described in greater detail herein below.Additionally, as used herein, light sensor 170 will generally refer toany light sensor shape, such as the spherical light sensor encapsulantof FIG. 23, and the cylindrical light sensor encapsulant of FIG. 26unless indicated otherwise.

Referring now to FIG. 27, a graph illustrating frequency response of thehuman eye is shown. Curve 610 represents the relative photopic ordaylight frequency response of the human eye. Curve 612 represents therelative scotopic or night frequency response of the human eye. Inaddition to being more sensitive to light intensity, scotopic response612 is shifted more towards violet than photopic response 610.

Referring now to FIG. 28, a graph illustrating frequency response of atypical light transducer is shown. The relative frequency response of atypical photodiode light transducer 178 is shown as curve 620. Whencompared to photopic response curve 610 or scotopic response curve 612,the frequency response of exposed light transducer 178 containssignificantly more infrared sensitivity. Depending upon the application,a filter may be placed before or incorporated into sensor 170 so thatthe output of exposed light transducer 178 more closely resembles adesired frequency response. The type of filtration required for lightsensor 170 will depend on the application in which the sensor is used.

Referring now to FIG. 29, a light sensor package wherein the enclosureincorporates a filter is shown. Window 174 in enclosure 172 includesfilter 630 operative to attenuate some components of light rays 570striking exposed light transducer 178. For example, filter 630 may be aninfrared filter such as a hot mirror commercially available from OpticalCoating Laboratories, Inc. of Santa Rosa, Calif. A lens (not shown) maybe placed in front of infrared filter 630 to control the image focusedon the transducer. Other examples of filters are described in U.S. Pat.No. 4,799,768 to Gahan and U.S. Pat. No. 5,036,437 to Macks.

It is envisioned that the filter 630 could be provided for the sensor170 using other constructions. For example, a separate filter (notshown) can be mounted in a common housing with the sensor 170 at aposition in front of the light sensor 170. For example, thin glassbandpass filters such as the BG28 or BG18 filters commercially availablefrom Schott Glass Technologies, Inc. of Duryea, Pa., could be employed.These filters reduce the infrared sensitivity of light sensor 170. Inyet other embodiment, the spectral characteristics of light sensor 170may be modified by material embedded into enclosure 172, or a thinapplique attached to the surface of the sensor encapsulant using anadhesive, or by directly depositing a filter onto semiconductor die 572.

A method by which an interference filter can be directly deposited ontoa semiconductor light sensor 170 will now be described with respect toFIGS. 30a through 30 d. In the first step, a photoresist is depositedover the over the entire wafer. The photoresist may be any suitablecommercially available photoresist material. The photoresist is thenpatterned to cover only those areas on the surface of the waferrequiring protection from the optical coating deposition such as thebonding pad, as shown in FIG. 30b. The optical film coating 579 is thenapplied to the surface of the die 572 as shown in FIG. 30c. The thinfilm 579 is deposited directly on the light sensor in multiple layers.The first layer of the interference filter can be a silicon layer 50 to80 nm thick, and preferably 65 nm thick. The second layer if theinterference filter is a layer of silicon dioxide, 100 to 200 nm thick,and preferably 145 nm thick. The third layer of the interference filteris a silicon layer 50 to 80 nm thick, and preferably 60 nm thick. Thethird layer of the interference filter is a layer of silicon dioxide 100to 200 nm thick, and preferably 140 nm thick. The fifth layer of theinterference filter is a thick layer of silicon dioxide to provideprotection, and may be 200 to 500 nm thick. After all five layers aredeposited, the photoresist is lifted off using a conventional lift offprocess, leaving the film deposited over the light sensitive region, butnot over the bonding pads, as shown in FIG. 30d. The resulting die canbe encapsulated to provide conventional packaging, such as the T 1¾package of FIG. 23. The interference filter described above will filterlight above 650 nm. Other materials could be applied in a similar mannerto provide other filter characteristics.

Referring now to FIG. 31, a graph of the frequency response of a windowfilm that may be applied to the light sensor filter is shown. A filmwith desired frequency characteristics such as, for example, XIR-70 fromSouthwall Technologies of Palo Alto, Calif., may be placed onto thewindow of light sensor 170. The spectrum of such a film is shown bycurve 640. An adhesive such as, for example, 9500 PC from 3M Corporationof Minnesota, is affixed to the film. This adhesive film may then beattached to the surface of light sensor 170. Referring now to FIG. 32,curve 650 illustrates the response of light sensor 170 onto which hasbeen placed an adhesive film having the frequency response shown bycurve 640 in FIG. 31.

Having described the general system operation as well as describing thesensor in detail, the system will now be described in greater detailthrough some specific examples. Referring first to FIG. 33, anautomatically dimmed rearview mirror 24,26 is shown that employs a lightsensor. A dimming element, shown generally by 50, includes variabletransmittance element 52 and reflective surface 54. Dimming element 50is constructed such that reflective surface 54 is viewed throughvariable transmittance element 52. Dimming element 50 exhibits variablereflectance of light in response to dimming element control signal 56.Forward ambient light sensor 58 is positioned to receive forward ambientlight 32 from generally in front of vehicle 20. Forward ambient lightsensor 58 produces discrete ambient light signal 60 indicating theamount of forward ambient light 32 incident on forward ambient lightsensor 58 over an ambient light integration period. Ambient light can bemeasured using the cyclical, varying integration periods shown in FIG.7. Glare sensor 62 is positioned to detect glare 34 from generallybehind vehicle 20 and may optionally be placed to view glare 34 throughvariable transmittance element 52. Glare sensor 62 produces discreteglare signal 64 indicating the amount of glare 34 incident on glaresensor 62 over a glare integration period. Control logic 66 receivesambient light signal 60 and determines an ambient light level. Controllogic 66 determines the glare integration period based on the level offorward ambient light 32. Control logic 66 receives glare signal 64 anddetermines the level of glare 34. Control logic 66 outputs dimmingelement control signal 56, setting the reflectance of dimming element 50to reduce the effects of glare 34 perceived by operator 22.

Either one of glare sensor 62 and forward ambient light sensor 58 or,preferably both sensors are implemented using a semiconductor lightsensor with variable sensitivity. Such sensors include light transducersthat convert incident light into charge as described herein above. Thischarge is collected over an integration period to produce a potentialthat is converted by sensor 58, 62 into a discrete digital output thatdoes not require analog-to-digital conversion prior to digitalprocessing in control logic 66. Eliminating the ADC conversion reducesthe cost of the microprocessor. As can be seen from FIG. 11, the light-to-pulse converter introduces a delay. The delay is the time differencebetween the sample period and the beginning of the measurement period420. This delay can be avoided using the analog circuit of FIG. 16a.However, the use of the analog circuit increases in two ways. First thenumber of wires in bus 164 may be doubled as a first wire will be usedfor the integration period input signal and a second wire will be usedas the analog output signal from differential amplifier 321. Secondly,the control logic will require an ADC to convert this analog signal to adigital signal usable by the digital control logic. Regardless ofwhether a digital or analog signal is generated, as mentioned above, onedifficulty with silicon-based sensors is the difference in spectralsensitivity between silicon and the human eye. Accordingly, light filter68 may be placed before or incorporated within ambient light sensor 50.Similarly, glare filter 70 may be placed before or incorporated withinglare sensor 62.

Filters 68, 70 attenuate certain portions of the spectrum that mayinclude visible light, infrared, and ultraviolet radiation such thatlight striking sensors 58, 62 combines with the frequency response oflight transducers within sensors 58, 62 to more closely approximate theresponse of the human eye and to compensate for tinting in vehiclewindows such as windshield 30. For an automatically dimming rearviewmirror, an important goal is to decrease the glare experienced byvehicle operator 20 in low light conditions. In order to preserve nightvision, which degrades rapidly when exposed to bright light,particularly in the range of scotopic curve 612, exposed lighttransducer 62, 58 should have a frequency response similar to scotopiccurve 612 such that the mirror attenuate light that would otherwisenegatively impact the night vision of the vehicle operator 22. If thisfilter is not used, exposed light transducer 62, 58 should at least havean attenuated infrared response. This is increasingly more important ashigh intensity discharge (HID) headlamps, which emit more blueish lightthan do incandescent or halogen lamps, gain in popularity. Accordingly,the filters 68 and 70 preferably provide a filter characteristic similarto scoptic curve 612.

Variable transmittance element 52 may be implemented using a variety ofdevices, as mentioned above. Dimming may be accomplished mechanically,using liquid crystal cells, suspended particle devices, oradvantageously using an electrochromic cell that varies transmittance inresponse to an applied control voltage. As will be recognized by one ofordinary skill in the art, the present invention does not depend on thetype or construction of dimming element 50. If dimming element 50includes electrochromic variable transmittance element 52, reflectivesurface 54 may be either incorporated into or external to variabletransmittance element 52.

Each interior rearview mirror 24 and exterior rearview mirror 26 mustinclude dimming element 50 for automatic dimming. Preferably, interiorrearview mirror 24 also includes control logic 66, light sensors 58, 62,and, if used, filters 68 and 70.

Referring now to FIG. 34, a block diagram of a rearview mirror systemwith interior and exterior rearview mirrors according to embodiments ofthe present invention is shown. Dimming element 50 in interior rearviewmirror 24 operates as described above. Each exterior rearview mirror 26includes exterior dimming element 80 having exterior variabletransmittance element 82 operative to attenuate light from rearwardscene 28 both prior to and after reflecting from exterior reflectivesurface 84. Exterior dimming element 80 provides variable reflectancebased on exterior dimming element control signal 86. Exterior dimmingelement 80 may operate in any manner described with regard to dimmingelement 50 and, preferably, is an electrochromic mirror. Exterior mirrorcontrol 88 generates exterior dimming element control signal 86.Exterior mirror control 88 may be part of exterior rearview mirror 26,interior rearview mirror 24, or may be located outside of any mirror 24,26. Various embodiments for controlling exterior dimming element 80depend on the amount of sensing and control to be included withinexterior rearview mirror 26.

In one embodiment, control logic 66 in interior rearview mirror 24determines exterior dimming element control signal 86 based on outputfrom forward ambient light sensor 58 and glare sensor 62. Exteriordimming element control signal 86 may be generated directly by controllogic 66 or exterior mirror control 88 may generate exterior dimmingelement control signal 86 based on a reflectance level calculated incontrol logic 66 and transmitted to exterior mirror control 88 throughinter-mirror signal 90.

In another embodiment, exterior rearview mirror 26 includes exteriorglare sensor 92 positioned to receive glare 34 from rearward scene 28and operative to output exterior glare signal 94 based on the amount ofglare 34 incident on glare sensor 92 over a glare integration period.Control logic 66 uses exterior glare signal 94 and ambient light signal60 to determine the reflectance level for exterior dimming element 80.Again, exterior dimming element control signal 86 may be generateddirectly by control logic 66 or may be developed by exterior mirrorcontrol 88 based on the reflectance level contained in inter-mirrorsignal 90. Exterior glare filter 96, similar to glare filter 70, may beplaced before exterior glare sensor 92 or built into exterior glaresensor 92 to provide exterior glare sensor 92 with a response closer tothe response of the human eye. Inter-mirror signal 90 and exterior glaresignal 94 may be in the form of a pulse width modulated signal, pulsedensity signal, serial data stream, or digitized and communicated overan automotive bus such as the CAN bus.

In still another embodiment, exterior glare sensor 92 produces exteriorglare signal 98 routed directly to exterior mirror control 88. Exteriormirror control 88 determines exterior dimming element control signal 86based on exterior glare signal 98 and the level of forward ambient light32 determined by control logic 66 and sent to exterior mirror control 88through inter-mirror signal 90.

In yet another embodiment, exterior rearview mirror 26 determinesreflectance for exterior dimming element 80 independent of glare 34 orforward ambient light 32 sensed by interior rearview mirror 24. In thisembodiment, exterior rearview mirror 26 operates as described above withrespect to interior rearview mirror 24.

Referring now to FIG. 35, a schematic diagram illustrating an embodimentof control logic for an automatically dimming interior rearview mirroris shown. The circuit represents an effective yet inexpensiveimplementation for automatically dimming interior rearview mirror 24.Similar logic may be used to implement automatically dimming exteriormirror control, headlamp control, moisture detection and moistureremoval control, electric window control, heating and cooling control,and the like. Control logic 66 utilizes a small, low costmicrocontroller, indicated by U1, such as the PIC16C620A from MicrochipTechnology, Inc. of Chandler, Ariz. Forward ambient light sensor 58communicates with microcontroller U1 through interconnection signal 186connected to microcontroller input RB0. Similarly, glare sensor 62communicates with microcontroller U1 through separate interconnectionsignal 186 a connected to microcontroller input RB2. As described above,each interconnection signal 186 carries integration period 158 frommicrocontroller U1 to light sensor 58, 62 as well as light intensityperiod 240 from light sensor 58, 62 to microcontroller U1. Resistor R29and capacitor C4 connected between V_(DD) and ground provide filteredpower for light sensors 58, 62.

Parallel resistor R15 and diode D5 are connected between V_(DD) and node708. Capacitor C12 is connected between node 708 and ground. Resistor R6connects common node 708 to input/MCLR of microcontroller U1. ComponentsD5, R15, R6, and C12 form a power-on reset circuit shown generally by710. Power is supplied to control logic 66 through ignition line 712.Diode D1 protects from reversed polarity on ignition line 712 and diodeD2 clamps the voltage derived from ignition line 712 to approximatelyfive volts. Capacitors C2, C7 and C11, resistor R3, and ferrite elementE1 form a power conditioning circuit shown generally by 714. Reverseline 716 is asserted when vehicle 20 is placed into reverse. CapacitorC10 and resistors R8, R9, and R27 form a reverse signal conditioningcircuit, shown generally by 718. Reverse signal conditioning circuit 718low pass filters reverse line 716 and provides electrostatic dischargeprotection for digital input pin RB6 on microcontroller U1.Microcontroller U1 uses the signal on reverse line 716 to clear variabletransmittance element 52 whenever vehicle 20 is placed in reverse.Microcontroller U1 is clocked by an RC oscillator formed by resistor R2connected between the OSC1 pin and V_(DD) and capacitor C1 connectedbetween the OSC1 pin and ground. Resistor R30 and LED D3 connected inseries between V_(DD) and open drain output RA4 of microcontroller U1form an indicator lamp that may be mounted on interior rearview mirror24 to alert operator 22 of the operating state of control logic 66.Switches S1 and S2 are connected to digital inputs RB1 and RB3,respectively, of microcontroller U1 to permit selecting control options.

Referring now to FIG. 36, a schematic diagram illustrating operation ofelectrochromic dimmer control is shown. A portion of control logic 66has been redrawn to more clearly illustrate control of electrochromicvariable transmittance element 52. Electrochromic variable transmittanceelement 52 can be implemented using any suitable variable reflectancedevice, and may for example comprise the electrochromic elementdescribed in U.S. Pat. No. 4,902,108 titled “Single-Compartment,Self-Erasing, Solution-Phase Electrochromic Devices, Solutions For UseTherein, And Uses Thereof” issued to Byker. Electrochromic variabletransmittance element 52 darkens in response to a control voltageapplied at input node 720. If the applied control voltage is removed,electrochromic variable transmittance element 52 will self discharge,passing an increasing amount of light. Electrochromic variabletransmittance element 52 may be rapidly cleared by shorting input node720 to ground.

Resistor R17 connects input node 720 to the emitter of Darlington pairQ10 at node 722. The collector of Q10 is connected to a power supplythrough current limiting resistor R5, which may for example have animpedance of 27 Ω. The base of Darlington pair Q10 is connected todigital output RB4 of microcontroller U1 through resistors R1 and R7.The base of Q10 is also connected to ground through resistor R4 andthrough resistor R7 and capacitor C16. Digital output pin RB4 is drivenby pulse output 724 in response to pulse control 726 generated bysoftware running on microcontroller U1. Pulse output 724 may produce apulse signal such as, for example, a pulse width modulated signal.Preferably, pulse output 724 functions as a switch, setting output pinRB4 to either a high voltage or a low voltage once during eachtransition period as described below. Capacitor C16 and resistors R1,R4, and R7 form a low pass filter, shown generally by 728, to smooth thesignal appearing on digital output RB4. This smoothing results in asubstantially constant applied control voltage at input node 720 for afixed desired control level. Additionally, the base-to-emitter diodedrops in Q10 together with the voltage divider formed between resistorR4 and the sum of resistors R1 and R7 set the operating voltage forelectrochromic variable transmittance element 52. Typical values forcomponents are 1 kΩ for R1 and R4, 100 Ω for R7, and 100 μF for C16.With digital output RB4 at 5 volts and nominal current draw byelectrochromic variable transmittance element 52, input node 720 isapproximately 1.2 Volts.

The performance of control logic 66 can be improved through feedback ofelectrochromic variable transmittance element 52 applied control voltageat input node 720. Microcontroller U1 includes comparison logic to causepulse output 724 to deliver a low voltage if the applied control voltageis greater than the desired control level and to deliver a high voltageotherwise. Typically, the high voltage is near V_(DD) and the lowvoltage is near ground. This comparison may be made by comparing adigital number representing the desired control level with the digitizedapplied control voltage obtained using an analog-to-digital converter(DAC). Alternately, DAC 730 and comparator 732 are used. DAC 730produces a desired voltage level on analog output AN2 in response to thedesired control level on DAC control 734 supplied by software running onmicrocontroller U1. Resistor R31 is connected between analog output AN2and node 736 and resistor R26 is connected between node 736 and ground.One input of comparator 732, at analog input AN3, is connected to node736. The other input of comparator 732, at analog input AN0, isconnected to input node 720. The output of comparator 732 indicates ifthe desired voltage level is greater than the applied control voltage.Values for resistors R31 and R26 are chosen so that the voltage at node736 is within the range of expected applied control voltages at inputnode 720 throughout the range of desired control voltages output fromDAC 730. Typical values for R31 and R26 are 390 kΩ and 200 kΩ,respectively.

Positive feedback is achieved by connecting resistor R24 between node736 and node 722. Resistor R17 is used to sense the drive currentthrough electrochromic variable transmittance element 52 and, hence, istypically a low value such as 10 Ω. Resistor R24 is typically a highvalue such as 1.3 MΩ. As the drive current through resistor R17increases, the voltage across resistor R17 increases pulling up thevoltage at node 736. This increase in the voltage on the positive inputterminal of comparator 732 has the regenerative effect of increasing theduty cycle from pulse output 724. This regenerative effect providesbetter system response at higher temperatures when electrochromicvariable transmittance element 52 has an increased current draw togetherwith an increase in maximum operating voltage. Positive feedback alsooffsets the effects of internal resistances within electrochromicvariable transmittance element 52.

Referring now to FIG. 37, a timing diagram illustrating electrochromicelement transmittance control is shown. During automatic dimmingoperation, software executing in microcontroller U1 is initiated attransition points, one of which is indicated by 740, separated by fixedtransition period 742. Desired control level 744 indicates the desiredlevel of transmittance for electrochromic variable transmittance element52. Desired control level 744 may be an analog value or, preferably, isa digital number determined by microcontroller U1. Desired control level744 is compared to applied control voltage 746 by comparison logic.Comparator 732 accepts applied control voltage 746 and the desiredcontrol voltage appearing at node 736. Comparator output 738 producesdifference signal 748, which is asserted when the desired voltage levelrepresenting desired control level 744 is greater than applied controlvoltage 746. Comparator output 738 is used to generate control signal750 on output RB4. If desired control level 744 is greater than appliedcontrol voltage 746, digital output RB4 is switched high. If desiredcontrol level 744 is less than applied control voltage 746, digitaloutput RB4 is switched low. Preferably, low pass filter 728 filterscontrol signal 750 to produce applied control voltage 746.

The duration of transition period 742 is set to inhibit flicker inelectrochromic element 52 that may be noticed, for example, by vehicleoperator 22. Transition period 742 may preferably be between two secondsand two microseconds. For the system described above, five millisecondsmay be used for transition period 742.

Referring now to FIG. 38, a graph indicating dimmer reflectance as afunction of applied control voltage is shown. Curve 754 plots percentreflectance for dimming element 50, containing electrochromic variabletransmittance element 52, as a function of applied control voltage 756.Curve 754 indicates a decrease in reflection from about 86% to about 8%as the applied control voltage is increased from about 0.2 V to about0.9 V. FIG. 38 also includes curve 756 illustrating current draw as afunction of applied control voltage 756 for typical electrochromicvariable transmittance element 52.

Referring again to FIG. 35, additional circuitry is provided to rapidlyclear variably transmissive electrochromic element 50. Transistor Q11 isconnected across variably transmissive electrochromic element 50 withcollector at node 720 and emitter at ground. The base of transistor Q11is connected through resistor R23 to digital output RB7. When digitaloutput RB7 is asserted, transistor Q11 turns on, acting as a switch torapidly discharge electrochromic variable transmittance element 52.Capacitor C6 is connected between the collector and base of transistorQ11 to reduce electromagnetic interference created as transistor Q11switches. Transistor Q12 is connected between the base of transistor Q10and ground and is also controlled by digital output RB7. Transistor Q11turns on with transistor Q12 to shut off transistor Q10 therebypreventing simultaneously attempting to darken and clear electrochromicvariable transmittance element 52. Resistor R7 is placed betweencapacitor C16 and the collector of transistor Q12 to limit the dischargecurrent from capacitor C16 through transistor Q12.

Referring now to FIG. 39, a flow diagram illustrating operation ofcontrol logic 66 for the rearview mirror 24,26 is shown. As will beappreciated by one of ordinary skill in the art, the operationsillustrated in FIG. 39 and other flow diagrams are not necessarilysequential operations. Also, though the operations are preferablyimplemented by software executing in microcontroller U1, operations maybe performed by software, hardware, or a combination of both. Thepresent invention transcends any particular implementation and aspectsare shown in sequential flow chart form for ease of illustration.

An ambient light reading is taken and the average ambient light isinitialized in block 760. When the automatic dimming system is initiallypowered up, the average ambient light level is initialized by taking afirst reading of forward ambient light 32 using forward ambient lightsensor 58. Acquiring an ambient light reading and the average ambientlight level are described with regard to blocks 762 and 770,respectively, below.

An ambient light reading is taken and the log of the ambient lightreading is found in block 762. The use of semiconductor forward ambientlight sensor 58 with integral charge collection produces ambient lightsignal 60 having good resolution over a wide range of ambient lightlevels 32. As described above, this is accomplished by taking variousreadings of forward ambient light 32 using different integration periods242, 248, 254 (FIG. 7). In one embodiment, four separate integrationperiods are used such as, for example, 600 μs, 2.4 ms, 9.6 ms, and 38.4ms. Each of these integration periods differs by a factor of four fromadjacent periods. Therefore, for example, the 2.4 ms integration periodcauses forward ambient light sensor 58 to be four times more sensitiveto forward ambient light 32 than does integrating with the 600 μsintegration period. Typically, the shortest integration pulse 242 isfirst used by forward ambient light sensor 58 to produce short signalpulse 244. The width of short signal pulse 244 is measured by controllogic 66. Since forward ambient light sensor 58 in complete darkness maystill develop short signal pulse 244 having a width less than 100 μs, aminimum threshold is set for accepting short signal pulse 244 asaccurately reflecting the level of forward ambient light 32. Typically,this threshold may be 300 μs. If short signal pulse 244 does not exceedthe threshold, the next longest integration period is used by forwardambient light sensor 58. If the longest integration time does not yielda suitably long signal pulse, forward ambient light 32 is at anextremely low level and mirror 24, 26 can be operated at maximumsensitivity to glare 34.

Using the logarithm of ambient light signal 60 permits the use of aninexpensive microcontroller such as U1, which may have only 8-bitinternal registers and no multiplication instructions. Sincemicrocontrollers are binary devices, base two logarithms require fewerinstructions to compute than base ten logarithms or natural logarithms.An algorithm is now described for obtaining an 8-bit, binary logarithmhaving the most significant four bits representing an integer part andthe least significant four bits a fractional part. The 8-bit ambientlight signal 60 resulting from the proper integration period is examinedbit-by-bit starting with the most significant bit until the first binaryone is found. The bit position containing the first binary one becomesthe integer portion of the logarithm. The four most significant bitsfollowing the bit position containing the first binary one become thefractional portion of the logarithm. This value is incremented byone-sixteenth to better approximate the logarithm. An example of thebinary logarithm approximation is now provided. Suppose ambient lightsignal 60 is determined to be 44 (00101101 in base two). The mostsignificant asserted bit is bit five, so the integer portion of theresultant value is binary 0101. The next four bits following bit fiveare 0110 so the fractional part of the resultant value is 0110 for atotal value of 0101.0110. After incrementing, the binary logarithmapproximation becomes 0101.0111.

Referring now to FIG. 40, a graph illustrating binary log approximationaccording to the above algorithm is shown. The binary logarithm isplotted for values of N between 1 and 255. Curve 790 shows the actualbinary logarithm. Curve 792 shows the approximated binary logarithm.

Ambient light signal 60 must be scaled to compensate for differentpossible integration periods. This may be accomplished by adding ascaling factor to the binary logarithm of ambient light signal 60. Forexample, if the longest integration time (38.4 ms) is used to measureforward ambient light 32, a scale factor of 0 is added. If the nextlongest integration time (9.6 ms) is used, a scale of factor of 2 isadded. If the next longest integration time (2.4 ms) is used, 4 isadded. If the shortest integration time (600 μs) is used, 6 is added.Since the largest value resulting from the binary logarithmapproximation is 8 (1000.0000), no overflow results from adding thescale factor.

Referring again to FIG. 39, the logarithm of the ambient light level iscompared to the day detect level in block 764. The day detect level is acalibrated value stored in microcontroller 66, read only memory,electronically erasable read-only memory, or the like, duringmanufacture. The day detect level is used to prevent dimming of, or tomore rapidly clear dimming element 50, during rapid transitions fromdark to bright such as if vehicle 20 emerges from a tunnel intodaylight. If the logarithm of forward ambient light 32 exceeds a presetday detect level, variable transmittance element 52 is cleared to setdimming element 50 to maximum reflectance in block 766. Processing isthen delayed in block 768. A wait loop is entered having a timesufficiently long to make the period between taking ambient lightreadings equal a constant ambient light loop delay. This period may be,for example, 400 ms. Following the wait in block 768, another reading offorward ambient light 32 is taken in block 762. If the logarithm offorward ambient light 32 does not exceed the day detect level, anaverage is obtained in block 770.

The average of the logarithm of ambient light level is determined inblock 770. Averaging readings first converted to the logarithm offorward ambient light 32 reduces the effect of a temporary bright lightin front of vehicle 20 from dramatically skewing the average reading ofan otherwise dark forward ambient light 32. A running average of the logof ambient light signals 50 may be obtained from a digital low passfilter such as is described by Equation 3:

y(n)=x(n)/64+63y(n−1)/64

where x(n) is the most recently obtained binary log approximation ofambient light signal 60 correctly scaled for the integration period,y(n−1) is the previous filter output, and y(n) is the current filteroutput. The use of averaged logarithms with analog light signals isdescribed in U.S. Pat. No. 5,204,778 titled “Control System ForAutomotive Rearview Mirrors” issued to Bechtel.

The average of the log of the ambient light level is compared to athreshold in block 772. The day detect level can be a calibrated valuestored in microcontroller 66, read only memory, electronically erasableread-only memory, or the like, during manufacture. If forward ambientlight 32 is sufficiently bright, vehicle operator 22 will not be dazzledby any reasonable amount of glare 34, allowing mirror 24, 26 to be setto maximum reflectance. Therefore, if the average of the log of ambientlight signal 60 is not less than the threshold, dimming element 50 iscleared in block 766 and the wait of block 768 is executed. If theaverage of the log of ambient light signals 50 is less than thethreshold, glare processing occurs beginning in block 774. Typically,the threshold used for comparison in block 772 is less than the daydetect level used in the comparison of block 764.

The glare integration period is determined in block 774. The integrationperiod for glare sensor 62 is determined based on ambient light signal60. The glare integration period is inversely proportional to the binaryantilogarithm of the average of the log of ambient light signal 60 asdescribed by Equation 4:

T_(G)(n)=antilog₂(K₁−y(n))−K₂

where T_(G)(n) is the integration period for glare sensor 62 for thefilter output at sample time n, K₁ is a multiplicative constant, and K₂is an additive constant. Constants K₁ and K₂ are determinedexperimentally. If the average of the log of ambient light signal 60 isbelow a certain level, a maximum glare sensitivity integration period isused.

A glare count is set in block 776. The glare count indicates the numberof glare readings taken between ambient light readings. The product ofthe glare count and the glare loop delay should equal the time betweentaking ambient light readings. For example, the glare count may be threeand the time between taking glare readings may be 133 ms.

A glare reading is taken in block 778. The pulse width returning fromglare sensor 62 as glare signal 64 is measured for the glare integrationperiod determined in block 774. It is envisioned that a pre-measurementof the glare reading can optionally be made, prior to taking themeasurement using the glare integration period determined in step 774,using a very short predetermined integration period similar to theintegration period resulting from pulse 240 used for the forward lightsensor, and may be an integration period as short as 30 to 40 μs. Ifthis short pre-measurement of glare is greater than a threshold level,the glare sensor is determined to be subject to a very high level oflight indicating that the rear sensor is saturated. The mirror may befully dimmed in response to this condition. If this pre-measurement doesnot exceed the threshold level, the processing will continue using theglare signal period determined in block 774.

The dimming element value is set in block 780. Glare signal 64 is usedto determine desired control level 744 setting the reflectance fordimming element 50. This may be accomplished, for example, through theuse of a look-up table which associates a lower reflectance with longerglare signal period. The precise relationship between the level of glare34 and the setting for variable transmittance element 52 depends uponfactors including the construction of mirror 24, 26, the configurationof vehicle 20, and preferential settings by operator 22. Desired controllevel 744 may be used to control variable transmittance element 52 asdescribed above. For example, a manual actuated mechanism may beprovided on the mirror to permit the user to adjust the relationshipbetween the glare level and the transmittance of element 52.

A check of the glare count is made in block 782. If the glare count iszero, the next ambient light reading is taken in block 762. If the glarecount is not zero, the glare count is decremented in block 784. A waitloop is then entered in block 786. The glare loop delay period is set sothat glare readings are taken at regular, predetermined intervals.

A system for detecting moisture on window 100 (FIG. 41), shown generallyby 102, includes light emitter 104 directed at window 100. Window 100may be windshield 30, rear window 36, or any other window on vehicle 20.Emitter 104 generates emitted radiation 106 that strikes window 100. Aportion of emitted radiation 106 is reflected from window 100 asreflected radiation 108. The intensity of reflected radiation 108 isbased on the amount of moisture on window 100.

Moisture light sensor 110 receives reflected radiation 108 andaccumulates charge in response to light 108 incident over an integrationperiod. Moisture light sensor 110 outputs light signal 112 based on theamount of light 108 incident on moisture light sensor 110 over the lightintegration period. The determination of the sensitivity for lightsensor 110 may be generated within moisture light sensor 110 using thesensor logic of FIG. 17, or may be supplied by light sensitivity signal114.

Ambient light 116 represents a source of noise that may mix withreflected radiation 108, affecting light signal 112. If window 100 isvehicle windshield 30, ambient light 116 may result from solarradiation, reflected sunlight, headlamps from oncoming vehicles, streetlights, and the like, and may come from forward ambient light 32,skyward ambient light 46, or other light direction depending on themounting and construction of sensor system 102. Ambient light 116 mayvary over a wide dynamic range. Removing the effects of ambient light116 improves the ability of moisture detecting system 102 to detectmoisture. Various designs may be used to reduce the amount of ambientlight 116 striking moisture light sensor 110 including channels andbaffles for deflecting light away from moisture light sensor 110 andsurfaces to reflect or refract ambient light 116 away from moisturelight sensor 110 as is known in the art.

Control logic 66 is connected to light emitter 104 and moisture lightsensor 110. Control logic 66 generates emitter signal 118 to turn on andoff light emitter 104. In an embodiment, control logic 66 receives afirst light signal 112 from moisture light sensor 110 with emitter 104turned off to obtain an indication of the level of ambient light 116.Emitter 104 is then turned on. Control logic 66 receives a second lightsignal 112 from moisture light sensor 110. The presence of moisture onwindow 100 is then determined based on first and second light signals112. If moisture is detected, control unit 66 may signal wiper control120 to activate windshield wiper motor 112 to move wipers 38 over window100. Control logic 66 may also signal defogger control 124 to activatedefogger 40. Control logic 66 may also signal defroster control 126 toactivate defroster 42. Other means for removing moisture from window 100may also be used within the spirit and scope of the present invention.

In the embodiment shown in FIG. 41, a single light emitter 104 and asingle moisture light sensor 110 are shown. However, it is within thespirit and scope of the present invention to include more than oneemitter 104, more than one moisture light sensor 110, or a plurality ofboth emitters 104 and sensors 110. Also, control logic 66 may be adaptedto control a wide variety of functions including closing windows,cleaning windows, activating lamps, and the like.

Referring now to FIG. 42, a ray diagram illustrating moisture detectionon an outside surface causing an increase in reflected light is shown.Window 100 has outer surface 130 and inner surface 132. In the absenceof moisture, emitted radiation 106 passes through inner surface 132 andouter surface 130 to become exiting ray 134. Moisture on outer surface130, such as droplet 136, causes at least some of emitted radiation 106to be reflected as reflected radiation 108, which is detected bymoisture light sensor 110 and converted to discrete light signal 112. Asecond light sensor, indicated by 110 a, may be positioned to detectmoisture on inner surface 132. Emitted radiation 106 may reflect offmoisture, such as fog or frost, on inner surface 132 producing reflectedradiation 108 a. Second moisture light sensor 110 a generates discretelight signal 112 a indicating the presence of moisture on inner surface132.

Referring now to FIG. 43, a ray diagram illustrating moisture detectionon an outside surface causing a decrease in reflected light is shown.Light emitter 104 is positioned such that emitted radiation 106 strikesinner surface 132 at an angle of incidence a allowing emitted radiation106 to pass through inner surface 132 and be totally reflected betweenouter surface 130 and inner surface 132 at least once before exiting asreflected radiation 108. To facilitate emitted radiation 106 enteringinner surface 132, emitter 104 is placed in input coupler 140, which isattached to inner surface 132. To facilitate reflected radiation 108exiting inner surface 132, moisture light sensor 110 is placed in outputcoupler 142, which is attached to inner surface 132. Input coupler 140and output coupler 142 are constructed of a material having an index ofrefraction similar to the index of refraction of window 100. For window100 constructed of glass and surrounded by air, the index of refractionis approximately 1.49 and the angle of incidence α must be greater than42°. If moisture, such as droplet 136, is present on outer surface 130or inner surface 132, total reflection between outer surface 130 andinner surface 132 is impaired, permitting exiting ray 144. Thisdecreases reflected radiation 108 received by moisture light sensor 110.Moisture light sensor 110 outputs discrete light signal 112 indicatingthe intensity of reflected radiation 108.

Input coupler 140 and output coupler 142 may be designed to reduce theeffect of ambient light 116 reaching moisture light sensor 110. Inparticular, reflective and refractive surfaces on coupler 140, 142 serveto direct reflected radiation 108 into moisture light sensor 110 anddirect ambient light 116 away from moisture light sensor 110. Flanges,baffles, shields, and the like may also block ambient light 116.Couplers may further be designed to prevent spurious reflected radiationfrom layers within window 100. Various designs for couplers 140, 142 arewell known in the art.

The designs represented by FIGS. 42 and 43 may be combined in a singledevice to provide greater sensitivity to moisture and to permitdetecting moisture on both outer surface 130 and inner surface 132. Foruse in detecting moisture on windshield 30, light emitter 104 andmoisture light sensor 110 are preferably mounted to monitor moisture ina region of windshield 30 wiped by windshield wipers 38. Mountinglocations include within or beside the interior rearview mirror mountingfoot or just above the dashboard.

Referring now to FIG. 44, a flow diagram illustrating operation ofcontrol logic for automatically removing moisture from a vehicle windowis shown. Operations may be executed using control logic 66 as describedabove or similar circuitry. The present invention transcends anyparticular implementation and aspects are shown in sequential flow chartform for ease of illustration.

Moisture light sensor 110 a is read with light emitter 104 switched offto obtain a level of ambient light 116 in block 800. Emitter 104 isactivated and light sensor 110 a is read a second time to determine theamount of reflected radiation 108 a from interior surface 132 in block802. In an embodiment, the integration period for the second reading isbased on the level of ambient light obtained in block 800, such that thebrighter the previous ambient light measurement, the shorter theintegration period used in the current measurement. In anotherembodiment, the intensity of emitted radiation 106 from emitter 104 ismodified based on the level of light determined in block 800. The levelof intensity of emitted radiation 106 may be controlled by using a pulsewidth modulated voltage for emitter signal 118.

Light signal 112 a produced with emitter 104 turned on is compared tolight signal 112 a produced with emitter 104 turned off in block 804. Ifthe difference between light signal 112 a produced with emitter 104 onand light signal 112 a produced with emitter 104 off exceeds an interiorsurface threshold, one or more means for removing moisture from interiorwindow surface 132 are turned on in block 806. If the difference is notgreater than the interior surface threshold, a check is made todetermine if means for removing moisture from exterior window surface130 should be activated beginning with block 808.

In an embodiment of the present invention, the interior surfacethreshold, which can be a calibrated value, is based on the level ofambient light 116 obtained in block 800. In another embodiment, twothresholds are used. In addition to the interior surface threshold, asecond, greater threshold is used to determine if a check should be madeafter activating the means for removing moisture 38 from exterior windowsurface 130. If reflected radiation 108 a is too great, excessivemoisture is present on inside surface 132, and an accurate reading ofthe moisture on outer surface 130 cannot be obtained. If the level ofreflected radiation 108 a is between the two thresholds, the means forremoving moisture from interior window surface 132 is activated and thena check is made whether to activate means for removing moisture fromexterior window surface 130.

Moisture light sensor 110 is read with light emitter 104 switched off toobtain a level of ambient light 116 in block 808. Emitter 104 isactivated and light sensor 110 is read a second time to determine theamount of reflected radiation 108 from exterior surface 130 in block810. In an embodiment, the integration period for the second reading isbased on the level of ambient light obtained in block 808. In anotherembodiment, the intensity of emitted radiation 106 from emitter 104 ismodified based on the level of ambient light 116 obtained in block 808and on the level of reflected light 108 a detected by light sensor 110a.

Light signal 112 produced with emitter 104 on is compared to lightsignal 112 produced with emitter 104 off in block 812. In a preferredembodiment, the configuration of emitter 104 and light sensor 110described above is used. Hence, if the difference between light signal112 produced with emitter 104 on and light signal 112 produced withemitter 104 off is less than an exterior surface threshold, means forremoving moisture from exterior window surface 130 are turned on inblock 814. The check for activating means for removing moisture frominterior window surface 132 beginning with block 800 is then repeated.

In an embodiment, the comparison of block 812 includes the level ofreflected radiation 108 a off inner surface 132. This is becausereflected radiation 108 can be no greater than emitted radiation 106less reflected radiation 108 a. In another embodiment, the exteriorthreshold is based on the level of ambient light 116 obtained in block808.

Many other algorithms for determining the presence of moisture on awindow of vehicle 20 may be used within the spirit and scope of thepresent invention. Some of these algorithms are described in U.S. Pat.No. 5,796,106 to Noack; U.S. Pat. No. 5,386,111 to Zimmerman; U.S. Pat.No. 5,276,389 to Levers; U.S. Pat. No. 4,956,591 to Schierbeek et al.;U.S. Pat. No. 4,916,374 to Schierbeek et al.; U.S. Pat. No. 4,867,561 toFujii et al.; U.S. Pat. No. 4,859,867 to Larson et al.; U.S. Pat. No.4,798,956 to Hochstein; U.S. Pat. No. 4,355,271 to Noack; and U.S. Pat.No. RE. 35,762 to Zimmerman.

A moisture detection system may use emitter 104 having a principalemission band across any of the visible or invisible light spectrum.Moisture light detector 110 must be constructed based on the desiredspectrum emitted by emitter 104. A preferred spectrum is weighted to theinfrared range. Consequently, no filtration may be required for moisturelight detector 110, 110 a. Alternatively, a filter that limitsnon-infrared light may be used for the moisture detector.

Referring now to FIG. 45, a system for controlling headlamps is shown.Skyward ambient light sensor 150 is mounted to view light illuminatingthe view seen by operator 22. Preferably, skyward ambient light sensor150 is positioned to receive skyward ambient light 46 from an areagenerally above and in front of vehicle 20. Skyward ambient light sensor150 generates skyward ambient light signal 152 based on the amount oflight incident on skyward ambient light sensor over an integrationperiod. The integration period may be advantageously varied according tothe control signal of FIG. 7. Control logic 66 uses skyward ambientlight signal 152 to activate headlamp control circuitry 154 activatingone or more headlamps 44. Preferably, ambient light filter 156 filtersskyward ambient light 46 reaching skyward ambient light sensor 150 toattenuate infrared components of skyward ambient light 46. The filtercharacteristics of the ambient light filter 156 are shown in FIG. 48. Ascan be seen from FIG. 48, the filter has a peak response atapproximately 475 nm. Such a filter will be highly sensitive, capable ofdetecting light under both cloudless and cloudy conditions.Alternatively, the filter may be selected to provide the light sensor150 with a spectral response similar to photopic response curve 610. Thefilter should at least attenuate infrared light to be input to sensor150.

An advantageous embodiment permits compensating for weather conditionsin determining the state for headlamps 44. This is accomplished using asecond skyward ambient light sensor 158 with ambient light filter 160generating skyward ambient light signal 162 for control logic 66 isincluded. In this embodiment, the ambient light filters 156, 160attenuate different portions of skyward ambient light 46. As examples,one filter may be cyan and the other red or one may be blue and theother near infrared. Since the spectral composition of skyward ambientlight 46 is different on clear days than on cloudy days, the ratio ofthe incident light represented by ambient light signals 152 and 162 willgive an indication of the type of day. Thresholds for determining thestate of headlamps 44 can then be varied based on the determined ratio.

Referring now to FIG. 46, a graph illustrating the differences in thespectral content of ambient light on a cloudy day and ambient light on aclear day is shown. The spectral characteristics of skyward ambientlight 46 vary depending on weather conditions. A typical cloudless daymay have a spectrum, normalized to a relative intensity of 1.0 at 620nm, as shown by curve 820. A typical cloudy day may have a spectrum,normalized to a relative intensity of 1.0 at 620 nm, as shown by curve822. Comparing curves 820 and 822 shows that clear days have asignificantly blueish spectrum as compared to cloudy days. Since vehicleoperator 22 perceives dim ambient light 46 from a cloudless sky as beingbrighter than ambient light 46 of a similar intensity from a cloudy sky,this difference in spectral composition may be used to modify the one ormore thresholds used to control vehicle headlamps 44.

Referring now to FIG. 47, a flow diagram illustrating operation ofcontrol logic for automatically controlling vehicle headlamps is shown.Operations may be executed using control logic 66 as described above orsimilar circuitry. The present invention transcends any particularimplementation and aspects are shown in sequential flow chart form forease of illustration.

Skyward ambient light 46 is read using skyward ambient light sensor 150in block 830. Skyward ambient light 46 is read using skyward ambientlight sensor 158 in block 832. Light sensors 150, 158 filter ambientlight 46 through filters 156, 160 respectively. The spectralcharacteristics of filters 156, 160 are chosen so that ambient light 46detected by light sensor 150 is bluer than ambient light 46 detected bylight sensor 158. This may be accomplished, for example, by using cyanfilter 156 and red filter 160, blue filter 156 and infrared filter 160,or the like. Filters 156, 160 may be incorporated into light sensors150, 158 or may be separate elements as described above.

The relative cloudiness is estimated in block 834. In particular, theratio of the outputs from light sensors 150, 158 may be obtained toindicate the relative blue content of ambient light 46. This ratio isused to determine one or more thresholds in block 836. Each threshold isused as a basis of comparison to determine control of headlamps 44. Itis envisioned that the value may be calibrated. Calibration as used inthis application, can refer to a sensor or a threshold being calibratedusing a coefficient value stored in microcontroller 66, read onlymemory, electronically erasable read-only memory, or the like, duringmanufacture, which coefficient value can represent the ratio of astandard value to an actual measurement for a subject sensor exposed toknown light levels measured in a tester prior to, or after, beinginstalled in a circuit. It is envisioned that the control logic 66 willobtain thresholds from a look-up table, although they may be calculatedusing a formulae, or a combination of a look-up table and a formula.

The level of ambient light 46 is compared against a day threshold inblock 838. If the intensity of ambient light 46 is greater than the daythreshold, headlamps 44 are set to daylight mode. This may be turningheadlamps 44 off or setting headlamps 44 on at a daylight runningintensity. The output of either of light sensors 150, 158 may be used inthe comparison. In an alternative embodiment, a daylight threshold iscalculated for each light sensor 150, 158, with daylight running modeset if the intensity measured by either sensor 150, 158 exceeds itsthreshold. In another embodiment, daylight running mode is set if theoutput from both sensors 150, 158 exceeds their respective thresholds.

If the level of ambient light 46 is less than the day threshold, acomparison is made with the night threshold in block 842. If the levelof ambient light 46 is greater than the night threshold, headlamps 44are set to low beam mode in block 844. If not, headlamps 44 are set tohigh beam mode in block 846. While the headlamp control system describedby FIG. 44 shows three states for headlamps 44, one of ordinary skill inthe art will recognize that the present invention may be used in othersystems, including dual state headlamps 44 and continuously variableheadlamps 44.

It is further envisioned that a skyward sensor 150 and/or 158 can beused in combination with forward sensor 58 to detect a condition underwhich the headlights should be turned on without delay. For example,when vehicle 20 enters a tunnel. It is desirable for the headlights toturn ON immediately upon the sky sensor detecting a night condition, asopposed to subjecting the change to a delay, when entering a tunnel. Atunnel can be detected using a sky ambient light sensor looking througha lens with a narrow focus and the forward sensor looking through a lenswith a broad focus. For such an embodiment, 156 (FIG. 7) can comprise alens providing a narrow focus for sky sensor 150 and 68 can comprise alens providing a wide field of view for sensor 58. It is envisioned thatthe lenses could be incorporated into the encapsulant shapes of thesensor or provided by discrete lenses positioned in front of the sensorsto control the field of view for the sensors. When the forward sensor 58detects a darker image than the sky sensor 150, the control unit mayanticipate a tunnel. Under such conditions, as soon as the sky sensordetects night conditions, the headlights will turn ON with no delay or avery short delay, such as a delay of 1-2 seconds. Under otherconditions, such as where the forward sensor 58 detects light, it is maybe desirable for the system to delay for 10-30 seconds turning theheadlights ON so that the headlights do not flash ON and OFF.

In particular, in one embodiment, a high threshold and a low thresholdare used for the sky sensor. The forward ambient light sensor 58 can beused for selecting the timing adjustments such that the delay forchanging the headlight state is dependent upon the forward measurementthrough light sensor 58. The short delay for transitioning from OFF toON can be 1 second, such that if the sky sensor 150 measurement dropsbelow the low threshold for more than 1 second, the headlights will turnON. The long delay for transitioning the headlight from OFF to ON can be15 seconds, such that if the sky sensor 150 measurement drops below thelow threshold for more than 15 seconds, the headlights will turn ON. Theshort delay for transitioning from ON to OFF can be five seconds, suchthat if the sky sensor 150 measurement is above the high threshold formore than five seconds, the headlights will turn OFF. The long delay fortransitioning from ON to OFF can be 15 seconds, such that if the skysensor 150 measurement remains above the high threshold for more than 15seconds, the headlights will turn OFF. The ON short period will beinitiated when the forward sensor 58 detects darkness while the skyambient sensor detects light conditions and the lights are OFF. The OFFshort period will be initiated when the forward sensor 58 detectsdaylight conditions while the sky sensor detects night conditions andthe lights are ON. The long delays can be used for other conditions.Headlights ON refers to nighttime lights (e.g., high or low beams) andheadlights OFF refers to daylight lights (e.g., no headlights ordaylight running lights). The low threshold can correspond to 1300 to1500 lux seen by the sky sensor. The high threshold can correspond to1800 to 2100 lux seen by the sky sensor. The ratio of the high to lowthresholds can be 1.3 to 1.5. It is further envisioned that if eitherthe forward sensor 58 or sky sensor 150 detects a light level below avery low level, such as 40 to 100 lux, the headlamps will switch onwithout significant delay regardless of any other sensed conditions. Itis also envisioned that the time periods described herein can beproportional to the vehicle's speed, such that the faster the vehicle istraveling, the shorter will be the delays.

As illustrated in FIG. 2, the mirror can include skyward sensors 150,158 on one end of mirror 24 and skyward sensors 150′, 158′ on the otherend of the mirror. It will be recognized that cars are manufactured fordrivers on either right side or left side of the vehicle depending uponthe country where the vehicle will be sold. The optional provision oftwo sets of sensors will result in one set being positioned on the endof the mirror closest to the window regardless of whether the mirror isinstalled in a vehicle having right side or left side driver operation.In operation, the control logic 66 will monitor the outputs from sensors150, 150′ 158, 158′ to determine which of the light sensors iscollecting more light in high ambient light conditions while the vehicleis traveling at a relatively high speed. The side of the mirrorcontaining the sensors with the highest light output will be used forthe ambient sky sensors. The other light sensor outputs will not be usedas the vehicle roof will shade them. In this manner the vehicle canautomatically detect whether the mirror is angled for a driver on theright or left side of the vehicle.

The use of cylindrical light sensor 170′ to implement the glare sensor62 orientated with the longitudinal axis horizontal provides significantadvantages for the automatic control of the electrochromic mirror. Thelens radius r (FIG. 26a) for this sensor can for example be 1.25 mm,producing a focal distance f of 2.5 mm, and the distance d between theexposed surface of the light transducer and the tip of the light sensorencapsulant can be 2.15 mm. The glare sensor 62 encapsulant can betransparent, having no diffusant therein. In particular, with the glaresensor positioned in the rearview mirror housing such that thelongitudinal axis of the cylindrical lens is oriented horizontally, awide horizontal viewing angle is achieved.

Of particular advantage is the off axis light sensitivity distributionof the lens 170′, which is shown in FIG. 49. In FIG. 49, the center axiscorresponds to the center of the transducer region 532. As can be seen,the cylindrical lens has high off-axis sensitivity along itslongitudinal axis. This is better illustrated in the rectangular view ofthe sensitivity curve, shown in FIG. 50. The peak off-axis sensitivityoccurs at an angle of approximately 50. This characteristic can be usedto improve detection of light from a passing vehicle which is ofparticular interest when the inside mirror controls the outside mirror.In particular, a passing vehicle's headlights will be off axis from theglare sensor located in the interior rearview mirror 24 even though itis shinning on the exterior rearview mirror 26. A conventional glaresensor located on the interior mirror will detect diminished light fromthe passing vehicle, and thus increase the mirror reflectance, when thelights from the passing vehicle no longer shines directly through therear window. The improved glare sensor 170′ has increased sensitivity tooff-axis light, and thus will be increasingly sensitive to lights withinviewing angle β. Thus, the reduced reflectivity of mirror 26 will bemaintained until the passing vehicle headlights are no longer visible tooperator 22 through mirror 26. Those skilled in the art will recognizethat the off axis distribution of the light sensors can be significantlyreduced by adding a diffusant or diffusing projections to theencapsulant, which is preferably done if the cylindrical lens sensor isused to implement ambient sensors 58, 150, 150′, 158, 158′.

In addition to separately controlling headlamps 44, automatic dimming ofmirrors 24, 26, and various means for removing moisture from windowssuch as wipers 38, defogger 40, defroster 42, and the like, benefit maybe achieved by combining light sensors 170 and control logic 66 fromdifferent applications. For example, control logic 66 can control thestate of headlamps 44 based on the level of light detected by at leastone sky ambient light sensor 150, 158. Control logic 66 may also controldimming of at least one rearview mirror 24, 26 based on levels of lightdetected by forward ambient light sensor 58 and glare light sensor 62.Control logic 66 may then also turn ON headlamps 44 when the level oflight detected by forward ambient light sensor 58 is below a thresholdlevel. This would turn ON headlamps 44 in situations such as tunnels orextended overpasses when overhead lighting may provide sufficient lightdetected by sky ambient light sensor 150, 158 to turn headlamps 44 off,but the area in front of vehicle 20 is relatively dimly lit.

In another example, control logic 66 determines the amount of moistureon a cleared area of a window of vehicle 20, such as windshield 30 orrear window 36, based on the output from at least one moisture sensor102. Control logic 66 controls means for removing moisture 38, 40, 42based on the determined amount of moisture. Control logic 66 furthercontrols the dimming of rearview mirror 24, 26 based on the amount ofmoisture and the levels of light detected by forward ambient lightsensor 58 and glare light sensor 62. This would permit control logic 66to undim mirror 24, 26 if a window through which light was received byforward ambient light sensor 58 or glare light sensor 62 was covered bymoisture such as frost, snow, fog, and the like. Also, for a windowcleaned by wipers 38, readings from forward ambient light sensor 58 orglare light sensor 62 may be ignored during intervals when one of thewipers 38 passes in front of light sensor 58, 62.

In still another example where control logic 66 determines the amount ofmoisture on a cleared area of a window of vehicle 20 and controls meansfor removing moisture 38, 40, 42, the control of headlamps 44 may bebased on detected moisture as well as the level of light detected by oneor more sky ambient light sensors 150, 158. Again, this would permitcontrol logic 66 to set headlamps 44 to a predetermined state if awindow through which light was received by forward skyward light sensor150, 158 was covered by moisture. Also, for a window cleaned by wipers38, readings from skyward ambient light sensor 150, 158 may be ignoredduring intervals when one of the wipers 38 passes in front of lightsensor 150, 158.

The present invention may be readily adapted to controlling otherequipment on vehicle 20 besides or in addition to headlamps 44,automatic dimming of mirrors 24, 26, and various means for removingmoisture from windows 38, 40, 42. For example, electrically poweredwindows, sunroofs, moon roofs, convertible tops, and the like may beautomatically closed when moisture such as rain is detected. Also,various lighting in addition to headlamps 44, such as running lights,park lights, puddle lights, courtesy lights, dashboard lights, and thelike may be automatically controlled based on one or more of ambientlighting conditions, the detection of moisture, the running state ofvehicle 20, and the like. The state of passenger compartment heating andcooling systems, including air conditioning, heater, vent positions,windows, and the like may be automatically controlled based on one ormore of ambient lighting conditions, the detection of moisture, therunning state of vehicle 20, internal temperature, external temperature,and the like.

Control logic 66 for receiving light signals 164 from multiple lightsensors 170 and generating control signals 166 for equipment of vehicle20 may be in one housing or may be distributed throughout vehicle 20.Elements of control logic 66 may even be included within light sensors170. Elements of control logic 66 may be interconnected through avariety of means including discrete wiring, buses, optical fiber, radio,infrared, and the like. Control logic 66 may comprise many cooperatingprocessors or a single multitasking processor. Operations may beimplemented in software, firmware, custom hardware, discrete logic, orany combination. The present invention does not depend on the method ormeans of implementing control logic 66.

It is envisioned that outside fog of the type requiring activation offront and/or rear fog lights could be automatically detected using areflected light detection system substantially similar to that providedfor the moisture detector. To detect such outside fog, a light sourceand sensor are spaced by a distance such that light from the emitterthat will be detected by the sensor is reflected from a point severalmeters from the vehicle. Under circumstances where the detectedreflected light level is substantially constant, and greater than athreshold level, and continuously detected over a substantial period oftime, front and/or rear vehicle fog lamps can be turned onautomatically.

Thus it can be seen that improved equipment control system is disclosed.The system is easier to manufacture since variations in the performanceof the light sensors can be compensated for in the microcontroller. Themirror is readily manufacturable by automated means. Additionally, thesystem can be provided at a lower cost as low cost control logic can beutilized. The system reliably detects light over a wide light range andwith significantly reduced temperature dependence.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, it is intended that thefollowing claims cover all modifications and alternative designs, andall equivalents, that fall within the spirit and scope of thisinvention.

What is claimed is:
 1. A system for automatically controlling equipmentin an automotive vehicle, each piece of vehicle equipment controlled byan equipment control signal, the system comprising: at least onesemiconductor light sensor, each semiconductor light sensor operative tooutput a discrete light signal based on light incident over a variableintegration period; and a control logic in communication with thevehicle equipment and the at least one semiconductor light sensor, thecontrol logic operative to generate at least one equipment controlsignal based on the discrete light signal, wherein the at least onelight sensor comprises: a light transducer exposed to light, the lighttransducer operative to accumulate charge in proportion to lightincident over the integration period; and a sensor logic incommunication with the exposed light transducer, the sensor logicoperative output the discrete light signal according to the accumulatedexposed light transducer charge.
 2. A system for automaticallycontrolling vehicle equipment as in claim 1 wherein the at least onelight sensor further comprises a light transducer shielded from ambientlight, the shielded light transducer operative to accumulate charge inproportion to noise over the integration period, and wherein the sensorlogic is farther operative to output the discrete light signal based onthe difference between the measured accumulated exposed light transducercharge and the measured accumulated shielded light transducer charge. 3.A system for automatically controlling vehicle equipment as in claim 1,wherein the sensor logic is operative to (a) determine the lightintegration period prior to beginning integration, (b) reset the chargeaccumulated in the exposed light transducer at the beginning of thedetermined light integration period, (c) measure the charge accumulatedby the exposed light transducer over the determined light integrationperiod, and (d) output a pulse having a width based on the measuredaccumulated exposed light transducer charge.
 4. A system forautomatically controlling vehicle equipment as in claim 3 wherein the atleast one light sensor further comprises a comparator with one inputconnected to the exposed light transducer and the other input connectedto a switched capacitor circuit, the switched capacitor circuitoperative to charge a capacitor to a fixed voltage when the switch isclosed and to discharge the capacitor at a constant rate when the switchis open, wherein the sensor logic is further operative to close theswitch during the determined light integration period and open theswitch after the determined light integration period, thereby creatingthe pulse at the comparator output.
 5. A system for automaticallycontrolling vehicle equipment as in claim 4 wherein the at least onelight sensor further comprises a second comparator with one inputconnected to a threshold voltage and the other input connected to theswitched capacitor circuit, the second comparator output operative toinhibit output of the determined pulse if the capacitor voltage is lessthan the threshold voltage.
 6. A system for automatically controllingvehicle equipment as in claim 3 wherein the at least one light sensorfurther comprises a light transducer shielded from ambient light, theshielded light transducer substantially similar to the exposed lighttransducer, the shielded light transducer operative to accumulate chargein proportion to noise over the integration period, wherein the sensorlogic is further operative to: reset the charge accumulated in theshielded light transducer at the beginning of the determined lightintegration period; measure the charge accumulated by the shielded lighttransducer over the determined light integration period; and output apulse having a width based on the difference between the measuredaccumulated exposed light transducer charge and the measured accumulatedshielded light transducer charge.
 7. A system for automaticallycontrolling vehicle equipment as in claim 1, wherein the at least onelight sensor further comprises an enclosure having a window forreceiving light, the light transducer being an exposed light transducerdisposed within the enclosure, the exposed light transducer operative toaccumulate charge in proportion to light received through the windowincident on the exposed light transducer and wherein the sensor logicbeing disposed within the enclosure, the sensor logic in communicationwith the exposed light transducer, the sensor logic operative to receivean integration signal and to output a light signal based on the lightincident on the exposed light transducer during a duration determinedfrom the integration signal.
 8. A system for automatically controllingvehicle equipment as in claim 1, wherein the at least one light sensorfurther comprises: an enclosure having a window for receiving light, theenclosure admitting a power pin, a ground pin, and a signal pin; thelight transducer being an exposed light transducer disposed within theenclosure, the exposed light transducer operative to accumulate chargein proportion to light received through the window incident on theexposed light transducer; a light-to-pulse circuit disposed within theenclosure and in communication with the exposed light transducer, thepower pin, and the ground pin, the light-to-voltage circuit operative tooutput an output pulse, the output pulse width based on chargeaccumulated by the exposed light transducer over an integration period;and the sensor logic disposed within the enclosure, the sensor logic incommunication with the light-to-pulse circuit, the power pin, the groundpin, and the signal pin, the sensor logic operative to: (a) receive anintegration pulse on the signal pin, (b) determine the integrationperiod based on the width of the integration pulse, and (c) output theoutput pulse on the signal pin.
 9. A system for automaticallycontrolling vehicle equipment as in claim 8 wherein the control logiccomprises at least one signal pin connected to the signal pin of the atleast one light sensor, the control logic further operative to: set thecontrol logic signal pin to output mode; determine an integrationperiod; generate an integration pulse on the control logic signal pin,the width of the integration pulse based on the determined integrationperiod; set the control logic signal pin to input mode; receive the atleast one light sensor output pulse; and determine a light levelreceived by the at least one light sensor based on the light sensoroutput pulse.
 10. A system for automatically controlling vehicleequipment as in claim 1 further comprising: a housing operative to bepositionally adjusted relative to the vehicle, the housing containing atleast one of the at least one semiconductor light sensor; and a mirrordisposed within the housing, the mirror permitting a vehicle operator toview a scene generally behind the vehicle.
 11. A system forautomatically controlling vehicle equipment as in claim 1, wherein theat least one light sensor comprises: a lens operative to focus lightfrom a viewing area, the discrete light signal based on the intensity ofthe focused light; and an adhesive film disposed on the lens, theadhesive film operative to filter out components of the focused light.12. A system for automatically controlling vehicle equipment as in claim1, wherein the vehicle equipment comprises at least one headlamp andwherein the at least one light transducer comprises at least one ambientlight sensor positioned to receive light generally in front of and abovethe vehicle.
 13. A system for automatically controlling vehicleequipment as in claim 12 wherein the at least one ambient light sensorrestricts the amount of light collected from an angle generally beneaththe horizon.
 14. A system for automatically controlling vehicleequipment as in claim 13 wherein the at least one ambient light sensorcomprises at least one from a set including an asymmetric lens and ahousing to restrict the collected light.
 15. A system for automaticallycontrolling vehicle equipment as in claim 12 wherein the at least oneambient light sensor comprises an infrared filter.
 16. A system forautomatically controlling vehicle equipment as in claim 15 wherein theinfrared filter comprises a film adhered to the at least one lightsensor.
 17. A system for automatically controlling vehicle equipment asin claim 1, wherein the vehicle equipment comprises a rearview mirror,the mirror comprising a dimming element having a variably reflectivesurface, the degree of reflectivity based on the equipment controlsignal, and wherein the at least one semiconductor light sensor is atleast one from a set including an ambient light sensor positioned toreceive light generally in front of the vehicle and a glare sensorpositioned to view a scene generally behind a vehicle operator.
 18. Asystem for automatically controlling vehicle equipment as in claim 17wherein the glare sensor comprises a glare lens providing the glaresensor with a narrower field of view than the field of view of theambient light sensor, the glare lens further providing the glare sensorwith a higher optical gain than the optical gain of the ambient lightsensor.
 19. A system for automatically controlling vehicle equipment asin claim 17 wherein the dimming element is an electrochromic element.20. A system for automatically controlling vehicle equipment as in claim19 wherein the control logic generates the equipment control signal as aconstant voltage between transition points, the time between adjacenttransition points being a fixed transition period, wherein, at eachtransition point, the control logic outputs a high voltage if an actualelectrochromic element input voltage is less than a desiredelectrochromic element input voltage and outputs a low voltageotherwise.
 21. A system for automatically controlling vehicle equipmentas in claim 20 wherein the control logic comprises a low pass filteroperative to filter the equipment control signal to produce the actualelectrochromic element input voltage.
 22. A system for automaticallycontrolling vehicle equipment as in claim 20 further comprising a switchconnected across the electrochromic element, the control logic furtheroperative to close the switch when the actual electrochromic elementinput voltage exceeds the desired electrochromic element input voltageby more than a preset amount.
 23. A system for automatically controllingvehicle equipment as in claim 17 wherein the control logic is operativeto: determine an ambient light level based on the ambient light sensorsignal; and determine an ambient light sensor integration period basedon the ambient light level.
 24. A system for automatically controllingvehicle equipment as in claim 17 wherein the control logic is operativeto: determine an ambient light level based on the ambient light sensorsignal; and determine a glare sensor integration period based on theambient light level.
 25. A system for automatically controlling vehicleequipment as in claim 17 wherein the control logic is operative to:determine an ambient light level based on the ambient light sensorsignal; obtain the ambient light level as a binary number; determine afirst binary number portion based on the bit position of the mostsignificant binary one in the ambient light level binary number;determine a second binary number portion based on the bit patternfollowing the most significant binary one in the ambient light levelbinary number; determine as the ambient light level binary logarithm asthe concatenation of the first binary number portion and the secondbinary number portion; and determine a glare sensor integration periodbased on the binary logarithm of the ambient light level.
 26. A systemfor automatically controlling vehicle equipment as in claim 1, whereinthe vehicle equipment is at least one of a set comprising anelectrochromic mirror, a window wiper, a window defogger, a windowdefroster, and a headlamp, the equipment control signal based on thedetected presence of moisture, and wherein at least one semiconductorlight sensor is positioned to receive light through a vehicle window.27. A system for automatically controlling vehicle equipment as in claim1, wherein the vehicle equipment is at least one of a set comprising anelectrochromic mirror, a window wiper, a window defogger, a windowdefroster, and a headlamp, the equipment control signal based on thedetected presence of moisture, and wherein at least one semiconductorlight sensor is positioned to receive light from a light emitterdirected at a vehicle window, the resulting light signal based on thepresence of moisture on the window.
 28. A system for automaticallycontrolling vehicle equipment as in claim 27 wherein the light emitteremits light in the infrared range.
 29. A system for automaticallycontrolling vehicle equipment as in claim 27 wherein the presence ofmoisture causes an increase in the level of light received by the lightsensor from the light emitter reflected off the vehicle window.
 30. Asystem for automatically controlling vehicle equipment as in claim 27wherein the presence of moisture causes a decrease in the level of lightreceived by the light sensor from the light emitter reflected off thevehicle window.
 31. A system for automatically controlling vehicleequipment as in claim 27 wherein the control logic is operative todetect an ambient light level.
 32. A system for automaticallycontrolling vehicle equipment as in claim 31 wherein the control logicis operative to generate an integration period based on the detectedambient light level.
 33. A system for automatically controlling vehicleequipment as in claim 1, wherein the control of vehicle equipment isbased on detecting the presence of moisture on a window having an innersurface and an outer surface, the system further comprising an emitteroperative to emit light at the window, the at least one semiconductorlight sensor comprising a light sensor positioned to receive light fromthe emitter reflected from the window outer surface.
 34. A system forautomatically controlling vehicle equipment as in claim 33 wherein thecontrol logic is operative to: receive a first light signal from thelight sensor with the emitter turned off; turn on the emitter; receive asecond light signal from the light sensor; and determine the presence ofmoisture based on the first light signal and the second light signal.35. A system for automatically controlling vehicle equipment as in claim34 wherein the at least one semiconductor light sensor comprises asecond light sensor positioned to receive light from the emitterreflected from the window inner surface, the control logic furtheroperative to: receive a third light signal from the second light sensorwith the emitter turned off; turn the emitter on; receive a fourth lightsignal from the second light sensor; and determine the presence ofmoisture on the inner surface based on the third light signal and thefourth light signal.
 36. A system for automatically controlling vehicleequipment as in claim 1, wherein the at least one semiconductor lightsensor is a plurality of light sensors, each light sensor detectingincident light within a target spatial distribution, the control logicgenerating the at least one equipment control signal independent of amapping of the discrete light signal to an area within the targetspatial distribution.
 37. A system for automatically controllingequipment in an automotive vehicle, each piece of vehicle equipmentcontrolled by an equipment control signal, the system comprising: atleast one semiconductor light sensor, each semiconductor light sensoroperative to output a discrete light signal based on light incident overa variable integration period; and a control logic in communication withthe vehicle equipment and the at least one semiconductor light sensor,the control logic operative to generate at least one equipment controlsignal based on the discrete light signal, wherein the at least onelight sensor is further operative to: receive an integration pulse, thewidth of the integration pulse determining the integration period; andgenerate an output pulse as the discrete output signal, the output pulsegenerated after receiving the integration pulse.
 38. A system forautomatically controlling vehicle equipment as in claim 37 wherein thedifference in time between the end of the integration pulse and thestart of the output pulse is indicative of the amount of thermal noisein the light sensor.
 39. A system for automatically controlling vehicleequipment as in claim 38 wherein the control logic is further operativeto disable automatic control of vehicle equipment if the amount ofthermal noise exceeds a preset limit.
 40. A system for automaticallycontrolling vehicle equipment as in claim 38 wherein the control logicis further operative to disregard the discrete light signal if theoutput pulse is not within a predetermined range.
 41. A system forautomatically controlling equipment in an automotive vehicle, each pieceof vehicle equipment controlled by an equipment control signal, thesystem comprising: at least one semiconductor light sensor, eachsemiconductor light sensor operative to output a discrete light signalbased on light incident over a variable integration period; and acontrol logic in communication with the vehicle equipment and the atleast one semiconductor light sensor, the control logic operative togenerate at least one equipment control signal based on the discretelight signal wherein the control logic determines an integration periodby cycling through a sequence of predetermined integration periods. 42.A system for automatically controlling equipment in an automotivevehicle, each piece of vehicle equipment controlled by an equipmentcontrol signal, the system comprising: at least one semiconductor lightsensor, each semiconductor light sensor operative to output a discretelight signal based on light incident over a variable integration period;and a control logic in communication with the vehicle equipment and theat least one semiconductor light sensor, the control logic operative togenerate at least one equipment control signal based on the discretelight signal, wherein the at least one light sensor has an input forreceiving a light integration period signal specifying the lightintegration period, the control logic further operative to determine thelight integration period based on at least one previously determinedlight level and to output the light integration period signal based onthe determined light integration period.
 43. A system for automaticallycontrolling vehicle equipment as in claim 42 wherein the lightintegration period is based on an ambient light level measurement.
 44. Asystem for automatically controlling equipment in an automotive vehicle,each piece of vehicle equipment controlled by an equipment controlsignal, the system comprising: at least one semiconductor light sensor,each semiconductor light sensor operative to output a discrete lightsignal based on light incident over a variable integration period; and acontrol logic in communication with the vehicle equipment and the atleast one semiconductor light sensor, the control logic operative togenerate at least one equipment control signal based on the discretelight signal, wherein the at least one light sensor has an input forreceiving a light integration period signal specifying the lightintegration period and wherein the light signal is a pulse having apulse width indicative of the light level, the control logic furtheroperative to: generate a sequence of integration period signals, eachintegration period signal in the sequence specifying a different lightintegration period; and determine the light level based on a resultinglight signal having a pulse width within at least one preset widththreshold.
 45. A system for automatically controlling equipment in anautomotive vehicle, each piece of vehicle equipment controlled by anequipment control signal, the system comprising: at least onesemiconductor light sensor, each semiconductor light sensor operative tooutput a discrete light signal based on light incident over a variableintegration period, and a control logic in communication with thevehicle equipment and the at least one semiconductor light sensor, thecontrol logic operative to generate at least one equipment controlsignal based on the discrete light signal, wherein the vehicle equipmentcomprises at least one headlamp and wherein the at least onesemiconductor light sensor comprises a first ambient light sensoradmitting light in a first band of frequencies and a second ambientlight sensor admitting light in a second band of frequencies differentthan the first band of frequencies.
 46. A system for automaticallycontrolling vehicle equipment as in claim 45 wherein the control logicis further operative to determine a first filtered ambient light levelfrom the light signal output from the first ambient light sensor;determine a second filtered ambient light level from the light signaloutput from the second ambient light sensor; determine a threshold basedon the first filtered ambient light level and the second filteredambient light level; and generate a headlamp control signal based on thethreshold and at least one of the first filtered ambient light level andthe second ambient light level.
 47. A system for automaticallycontrolling vehicle equipment as in claim 46 wherein the threshold isdetermined based on a ratio between the first filtered ambient lightlevel and the second filtered ambient light level.
 48. A system forautomatically controlling vehicle equipment as in claim 45 wherein thefirst ambient light sensor substantially passes light from a cloudlessday and the second ambient light sensor substantially passes light froma cloudy day.
 49. A system for automatically controlling vehicleequipment as in claim 45 wherein light in the first band of frequenciesincludes light from a cloudless day and light in the second band offrequencies includes light from a cloudy day.